Method and apparatus for transmitting and receiving R-PDCCH

ABSTRACT

A method and apparatus for transmitting and receiving a Relay Physical Downlink Control Channel (R-PDCCH) being a control channel for a relay node (RN) in a wireless communication system are disclosed. To transmit an R-PDCCH to a RN, a BS includes a processor for interleaving a predetermined number of Control Channel Elements (CCEs), mapping the interleaved CCEs to at least one Virtual Resource Block (VRB) configured for R-PDCCH transmission, mapping the at least one VRB to at least one Physical Resource Block (PRB), and a transmitter for transmitting the R-PDCCH to the RN through the at least one PRB.

This application is a 35 U.S.C. §National Stage Entry of InternationalApplication No. PCT/KR2011/004448, filed Jun. 17, 2011 and claims thebenefit of U.S. Provisional Application No. 61/356,024, filed Jun. 17,2010, U.S. Provisional Application No. 61/363,621, filed Jul. 12, 2010and Korean Application No. 10-2011-0058458, filed Jun. 16, 2011, all ofwhich are incorporated by reference in their entirety herein.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method and apparatus for transmitting andreceiving a Relay-Physical Downlink Control Channel (R-PDCCH).

BACKGROUND ART

Wireless communication systems have been widely deployed to providevarious types of communication services such as voice service or dataservice. In general, a wireless communication system is a multipleaccess system that supports communication with multiple users by sharingavailable system resources (e.g. a bandwidth, transmission power, etc.)among the multiple users. The multiple access system may adopt amultiple access scheme such as Code Division Multiple Access (CDMA),Frequency Division Multiple Access (FDMA), Time Division Multiple Access(TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), SingleCarrier Frequency Division Multiple Access (SC-FDMA), or Multi CarrierFrequency Division Multiple Access (MC-FDMA).

DISCLOSURE Technical Problem

An object of the present invention devised to solve the problem lies ona method for transmitting a Relay-Physical Downlink Control Channel(R-PDCCH).

Another object of the present invention devised to solve the problemlies on a method for receiving an R-PDCCH.

Another object of the present invention devised to solve the problemlies on an apparatus for transmitting an R-PDCCH.

A further object of the present invention devised to solve the problemlies on an apparatus for receiving an R-PDCCH.

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present invention are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present invention could achieve will be more clearlyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings.

Technical Solution

The object of the present invention can be achieved by providing amethod for transmitting an R-PDCCH being a control channel for a relaynode (RN) in a wireless communication system, including interleaving apredetermined number of Control Channel Elements (CCEs), mapping theinterleaved CCEs to at least one Virtual Resource Block (VRB) configuredfor R-PDCCH transmission, mapping the at least one VRB to at least onePhysical Resource Block (PRB), and transmitting the R-PDCCH to the RNthrough the at least one PRB.

The interleaving may further include permutation and the permutation maybe performed according to a column permutation pattern.

During the interleaving, the predetermined number of CCEs may be dividedand interleaved.

The VRB may be mapped to the PRB in a frequency-first manner. The VRBmay also be mapped to the PRB in a time-first manner. The size of theVRB may be equal to the size of a CCE.

The size of the VRB may be 8 Resource Element Groups (REGs). An index ofthe VRB may be mapped to a PRB index numbered at 1:1 according to apredetermined index order.

In another aspect of the present invention, provided herein is a BaseStation (BS) for transmitting an R-PDCCH being a control channel for arelay node (RN) in a wireless communication system, including aprocessor for interleaving a predetermined number of CCEs, mapping theinterleaved CCEs to at least one VRB configured for R-PDCCHtransmission, mapping the at least one VRB to at least one PRB, andmapping the PRB to a pre-allocated R-PDCCH area, and a transmitter fortransmitting the R-PDCCH to the RN through the at least one PRB.

The processor may further perform permutation according to a columnpermutation pattern during the interleaving. The processor may map theVRB to the PRB in a frequency-first manner. The processor may map theVRB to the PRB in a time-first manner. The processor may divide thepredetermined number of CCEs and interleave the divided CCEs. Theprocessor may map an index of the VRB to a PRB index at 1:1 according toa predetermined index order.

Advantageous Effects

In accordance with embodiments of the present invention, a Base Station(BS) can efficiently transmit an R-PDCCH to a Relay Node (RN) and the RNcan significantly improve communication performance using theefficiently allocated R-PDCCH.

It will be appreciated by persons skilled in the art that that theeffects that could be achieved with the present invention are notlimited to what has been particularly described hereinabove and otheradvantages of the present invention will be more clearly understood fromthe following detailed description taken in conjunction with theaccompanying drawings.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

In the drawings:

FIG. 1 illustrates physical channels and signal transmission on thephysical channels in a 3^(rd) Generation Partnership Project (3GPP)system.

FIG. 2 illustrates a radio frame structure in the 3GPP system.

FIG. 3 illustrates the structure of a downlink resource grid for theduration of one downlink slot.

FIG. 4 illustrates a downlink subframe structure in the 3GPP system.

FIG. 5 illustrates an uplink subframe structure in the 3GPP system.

FIG. 6 illustrates a method for mapping Virtual Resource Blocks (VRBs)to Physical Resource Blocks (PRBs).

FIGS. 7, 8 and 9 illustrate Resource Allocation (RA) of type 0, RA oftype 1 and RA of type 2, respectively.

FIG. 10 illustrates a wireless communication system having relays.

FIG. 11 illustrates backhaul transmission in a Multicast BroadcastSingle Frequency Network (MBSFN) subframe.

FIG. 12 is a diagram illustrating a signal flow for allocating resourcesfor a Relay Physical Downlink Control CHannel (R-PDCCH) and receivingthe R-PDCCH using the allocated resources according to an embodiment ofthe present invention.

FIG. 13 illustrates exemplary R-PDCCH interleaving;

FIGS. 14 to 18 illustrate methods for multiplexing R-PDCCHs withRelay-Physical Downlink Shared CHannels (R-PDSCHs) in resourcesallocated according to a Distributed VRB (DVRB) scheme according toembodiments of the present invention;

FIG. 19 illustrates an example of transmitting R-PDCCHs and R-PDSCHs;

FIGS. 20 and 21 illustrate an example of configuring R-PDCCH ResourceBlocks (RBs);

FIGS. 22, 23 and 24 illustrate exemplary operations for transmitting anR-PDCCH and performing associated blind decoding according to whetherinterleaving is applied to the R-PDCCH;

FIG. 25 illustrates an exemplary operation for mapping R-PDCCHs to PRBs;

FIG. 26 illustrates an example of R-PDCCH and R-PDSCH resourceallocation;

FIG. 27 illustrates exemplary R-PDCCH mapping in case ofinterleaving-off;

FIG. 28 illustrates an example of configuring different Search Space(SS) RBs or different SS RB Groups (RBGs) over time;

FIGS. 29 to 32 illustrate an example of configuring R-PDCCH SSsaccording to RA types;

FIGS. 33, 34 and 35 illustrate various examples of configuring anR-PDCCH SS within each RBG;

FIG. 36 illustrates an example of configuring an R-PDCCH Dedicated SS(DSS) and an R-PDCCH Common SS (CSS);

FIG. 37 illustrates exemplary R-PDCCH transmission according to a systemband;

FIGS. 38 to 42 illustrate exemplary mapping operations for R-PDCCHtransmission;

FIG. 43 illustrates an exemplary mapping operation for R-PDCCHtransmission;

FIG. 44 illustrates an example of blind decoding positions and frequencyareas for blind decoding, for interleaving depths of 4, 8, 12 and 16;and

FIGS. 45 and 46 illustrate other examples of blind decoding positionsand frequency areas for blind decoding, for interleaving depths of 4, 8,12 and 16.

BEST MODE

The configuration, operation, and other features of the presentinvention will readily be understood with embodiments of the presentinvention described with reference to the attached drawings. Embodimentsof the present invention are applicable to a variety of wireless accesstechnologies such as Code Division Multiple Access (CDMA), FrequencyDivision Multiple Access (FDMA), Time Division Multiple Access (TDMA),Orthogonal Frequency Division Multiple Access (OFDMA), Single CarrierFrequency Division Multiple Access (SC-FDMA), and Multi CarrierFrequency Division Multiple Access (MC-FDMA). CDMA can be implementedinto a radio technology such as Universal Terrestrial Radio Access(UTRA) or CDMA2000. TDMA can be implemented into a radio technology suchas Global System for Mobile communications (GSM)/General Packet RadioService (GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). OFDMA canbe implemented into a radio technology such as Institute of Electricaland Electronics Engineers (IEEE) 802.11 (Wireless Fidelity (Wi-Fi)),IEEE 802.16 (Worldwide interoperability for Microwave Access (WiMAX)),IEEE 802.20, and Evolved UTRA (E-UTRA). UTRA is part of Universal MobileTelecommunications System (UMTS). 3^(rd) Generation Partnership Project(3GPP) Long Term Evolution (LTE) is part of Evolved UMTS (E-UMTS) usingE-UTRA. LTE-Advanced (LTE-A) is an evolution of 3GPP LTE.

While the following description is given of embodiments of the presentinvention with the appreciation that the technical features of thepresent invention are applied to a 3GPP system, this is purely exemplaryand thus should not be construed as limiting the present invention.

FIG. 1 illustrates physical channels and signal transmission on thephysical channels in a 3GPP LTE system.

Referring to FIG. 1, when a User Equipment (UE) is powered on or entersa new cell, the UE performs an initial cell search involving acquisitionof synchronization with a Base Station (BS) (S101). For the initial cellsearch, the UE receives a Primary Synchronization CHannel (P-SCH) and aSecondary Synchronization CHannel (S-SCH), and acquires synchronizationwith the BS and information such as a cell Identity (ID) from the P-SCHand the S-SCH. Then the UE may receive a Physical Broadcast CHannel(PBCH) from the BS and acquire broadcast information within a cell fromthe PBCH.

Upon completion of the initial cell search, the UE may acquire morespecific system information by receiving a Physical Downlink ControlCHannel (PDCCH) and receiving a Physical Downlink Shared CHannel (PDSCH)according to information carried on the PDCCH (S102).

Meanwhile, if the UE initially accesses the BS or has no radio resourcesfor signal transmission, the UE may perform a Random Access (RA)procedure (S103 to S106). For the RA procedure, the UE may transmit apredefined sequence as a preamble on a Physical Random Access CHannel(PRACH) (S103 and S105) and receive a response message to the preambleon a PDSCH (S104 and S106). If the RA procedure is contention-based, theUE may additionally perform a contention resolution procedure.

After the above RA procedure, the UE may receive a PDCCH/PDSCH (S107)and transmit a Physical Uplink Shared CHannel (PUSCH)/Physical UplinkControl CHannel (PUCCH) (S108) in a general uplink/downlink signaltransmission procedure. Control information that the UE receives fromthe BS on a downlink or transmits to the BS on an uplink includes adownlink/uplink ACKnowledgment/Negative ACKnowledgment (ACK/NACK)signal, a Channel Quality Indicator (CQI), a Scheduling Request (SR), aPrecoding Matrix Index (PMI), and a Rank Indicator (RI). In the 3GPP LTEsystem, the UE may transmit control information such as a CQI, a PMI andan RI on a PUSCH and/or a PUCCH.

FIG. 2 illustrates a radio frame structure in the 3GPP system.

Referring to FIG. 2, a radio frame is 10 ms (307,200 T_(s)) in duration.The radio subframe is divided into 10 subframes, each subframe being 1ms long. Each subframe is further divided into two slots, each of 0.5 ms(15,360 T_(s)) duration. T_(s) represents a sampling time and is givenas T_(s)=1/(15 kHz×2048)=3.2552×10⁻⁸(about 33 ns). A slot is defined bya plurality of Orthogonal Frequency Division Multiplexing (OFDM) symbolsin time by a plurality of Resource Blocks (RBs) in frequency. One RB has12 subcarriers by 7 (6) OFDM symbols in the 3GPP LTE system. A unit timein which data is transmitted, known as Transmission Time Interval (TTI)may be defined as one or more subframes. This radio frame structure ispurely exemplary and thus the number of subframes, the number of slots,or the number of OFDM symbols in a radio frame may vary.

FIG. 3 illustrates the structure of a downlink resource grid for theduration of one downlink slot.

Referring to FIG. 3, a downlink slot includes 7 (or 6) OFDM symbols intime by N^(DL) _(RB) RBs in frequency. Because each RB has 12subcarriers, the downlink slot includes N^(DL) _(RB)×12 subcarriers infrequency. In the illustrated case of FIG. 3, the downlink slot has 7OFDM symbols and each RB includes 12 subcarriers, which does not limitthe scope and spirit of the present invention. For example, the numberof OFDM symbols per downlink slot depends on the length of a CyclicPrefix (CP). Each element in the resource grid is referred to as aResource Element (RE). An RE is a minimum time/frequency resourcedefined for a physical channel, indicated by one OFDM symbol index andone subcarrier index. Each RB includes N_(symb) ^(DL)×N_(sc) ^(RB) REswhere N_(symb) ^(DL) represents the number of OFDM symbols per downlinkslot and N_(sc) ^(RB) represents the number of subcarriers per RB. Thenumber of RBs per downlink slot, N^(DL) _(RB) depends on a downlinktransmission bandwidth set by a cell.

FIG. 4 illustrates a downlink subframe structure in the 3GPP system.

Referring to FIG. 4, a downlink subframe includes a plurality of (e.g.12 or 14) OFDM symbols. A plurality of OFDM symbols at the start of thedownlink subframe are used for a control region and the other OFDMsymbols of the downlink subframe are used for a data region. The size ofthe control region may be determined independently for each subframe.The control region carries scheduling information and other Layer1/Layer 2 (L1/L2) control information, whereas the data region carriesdata. Control channels include a Physical Control Format IndicatorCHannel (PCFICH), a Physical Hybrid automatic repeat request (ARQ)Indicator CHannel (PHICH), and a Physical Downlink Control CHannel(PDCCH). Traffic channels include a Physical Downlink Shared CHannel(PDSCH).

The PDCCH delivers information related to resource allocation fortransport channels, a Paging CHannel (PCH) and a Downlink Shared CHannel(DL-SCH), an uplink scheduling grant, and HARQ information to each UE oreach UE group. The PCH and the DL-SCH are delivered on the PDSCH.Therefore, a BS and a UE transmit and receive data on the PDSCH exceptfor predetermined control information or predetermined service data.Control information carried on the PDCCH is called Downlink ControlInformation (DCI). The DCI transports uplink resource allocationinformation, downlink resource allocation information, or uplinktransmission power control commands for UE groups. Table 1 belowillustrates DCI formats according to the contents of DCI.

TABLE 1 DCI Format Description DCI format 0 used for the scheduling ofPUSCH DCI format 1 used for the scheduling of one PDSCH codeword DCIformat 1A used for the compact scheduling of one PDSCH codeword andrandom access procedure initiated by a PDCCH order DCI format 1B usedfor the compact scheduling of one PDSCH codeword with precodinginformation DCI format 1C used for very compact scheduling of one PDSCHcodeword DCI format 1D used for the compact scheduling of one PDSCHcodeword with precoding and power offset information DCI format 2 usedfor scheduling PDSCH to UEs configured in closed- loop spatialmultiplexing mode DCI format 2A used for scheduling PDSCH to UEsconfigured in open-loop spatial multiplexing mode DCI format 3 used forthe transmission of TPC commands for PUCCH and PUSCH with 2-bit poweradjustments DCI format 3A used for the transmission of TPC commands forPUCCH and PUSCH with single bit power adjustments

DCI format 0 conveys uplink resource allocation information, DCI format1 to DCI format 2A are used to indicate downlink resource allocationinformation, and DCI format 3 and DCI format 3A indicate Transmit PowerControl (TPC) commands for UE groups. The BS determines a PDCCH formataccording to DCI for a UE and adds a Cyclic Redundancy Check (CRC) tocontrol information. The CRC is masked by a unique ID such as a RadioNetwork Temporary Identifier (RNTI) according to the owner or purpose ofthe PDCCH.

FIG. 5 illustrates an uplink subframe structure in the 3GPP system.

Referring to FIG. 5, a basic unit for LTE uplink transmission, a 1-mssubframe 500 includes two 0.5-ms slots 501. On the assumption of anormal CP, each slot has 7 symbols 502, each symbol being an SC-FDMAsymbol. An RB 503 is a resource allocation unit defined by 12subcarriers in frequency by one slot in time. The LTE uplink subframe islargely divided into a data region 504 and a control region 505. Thedata region 504 refers to communication resources used to transmit datasuch as voice data and packets, including a Physical Uplink SharedCHannel (PUSCH). The control region 505 refers to communicationresources used for each UE to transmit a downlink channel qualityreport, an ACK/NACK for a received downlink signal, and an uplinkscheduling request, including a Physical Uplink Control CHannel (PUCCH).A Sounding Reference Signal (SRS) is transmitted in the last SC-FDMAsymbol of a subframe in the time domain and in a data transmission bandin the frequency domain. SRSs transmitted in the last SC-FDMA symbol ofthe same subframe from a plurality of UEs can be distinguished by theirfrequency positions/sequences.

Now a description will be given of RB mapping. Physical Resource Blocks(PRBs) and Virtual Resource Block (VRBs) are defined. PRBs areconfigured as illustrated in FIG. 3. Specifically, a PRB is a set ofN_(symb) ^(DL) contiguous OFDM symbols by N_(sc) ^(RB) contiguoussubcarriers. PRBs are numbered from 0 to N_(RB) ^(DL)−1 in the frequencydomain. The relationship between a PRB number n_(PRB) and REs (k,l) in aslot is given by

$\begin{matrix}{n_{PRB} = \lfloor \frac{k}{N_{sc}^{RB}} \rfloor} & \lbrack {{Equation}\mspace{14mu} 1} \rbrack\end{matrix}$where k denotes a subcarrier index and N_(sc) ^(RB) denotes the numberof subcarriers in an RB.

A VRB is equal in size to a PRB. Two types of VRBs are defined,Localized VRBs (LVRBs) and Distributed VRBs (DVRBs). Irrespective of aVRB type, a pair of VRBs with the same VRB number n_(VRB) are mapped totwo RBs in the two slots of a subframe.

FIG. 6 illustrates a method for mapping VRBs to PRBs.

Referring to FIG. 6, LVRBs are mapped directly to PRBs such that thenumbers of the LVRBs, n_(VRB) is identical to the numbers of the PRBs,n_(PRB) (n_(VRB)=n_(PRB)). VRBs are numbered from 0 to N_(VRB) ^(DL)−1and N_(VRB) ^(DL)=N_(RB) ^(DL). In contrast, DVRBs are mapped to PRBsafter interleaving. More specifically, a DVRB may be mapped to a PRB asillustrated in Table 2. Table 2 lists RB gaps.

TABLE 2 Gap (N_(gap)) System BW 1^(st) Gap 2^(nd) Gap (N_(RB) ^(DL))(N_(gap,1)) (N_(gap,2))  6-10 ┌N_(RB) ^(DL)/2┐ N/A 11 4 N/A 12-19 8 N/A20-26 12 N/A 27-44 18 N/A 45-49 27 N/A 50-63 27 9 64-79 32 16  80-110 4816

N_(gap) denotes the frequency spacing between PRBs in the first andsecond slots of a subframe, to which VRBs with the same VRB number aremapped. The frequency spacing may be expressed as the number of PRBs. If6≦N_(RB) ^(DL)≦49, only one gap is defined (N_(gap)=N_(gap,1)). If50≦N_(RB) ^(DL)≦110, two gaps N_(gap,1) and N_(gap,2) are defined.N_(gap)=N_(gap,1) or N_(gap)=N_(gap,2) or is signaled through downlinkscheduling. DVRBs are numbered from 0 to N_(VRB) ^(DL)−1. IfN_(gap)=N_(gap,1), N_(VRB) ^(DL)=N_(VRB,gap,1) ^(DL)=2·min(N_(gap),N_(RB) ^(DL)−N_(gap)). If N_(gap)=N_(gap,2), N_(VRB) ^(DL)=N_(VRB,gap2)^(DL)=└N_(RB) ^(DL)/2N_(gap)┘·2N_(gap). min(A, B) represents the smallervalue between A and B.

Ñ_(VRB) ^(DL) consecutive VRB numbers form a VRB number interleavingunit. If N_(gap)=N_(gap,1), Ñ_(VRB) ^(DL)=N_(VRB) ^(DL). IfN_(gap)=N_(gap,2), Ñ_(VRB) ^(DL)=2N_(gap). VRB number interleaving maybe performed using four columns and N_(row) rows in each interleavingunit. Thus, N_(row)=┌Ñ_(VRB) ^(DL)/(4P)┐·P where P denotes the size of aResource Block Group (RBG). An RBG is defined as P consecutive RBs. VRBnumbers are written in a matrix row by row and read from the matrixcolumn by column. N_(null) nulls are inserted into the last N_(null)/2rows of the second and fourth columns, N_(null)=4N_(row)−Ñ_(VRB) ^(DL).The nulls are neglected during reading.

Conventional LTE resource allocations will be described below. FIGS. 7,8 and 9 illustrate control information formats for Resource Allocation(RA) of type 0, RA of type 1 and RA of type 2 and examples of resourceallocation according to the control information formats.

A UE interprets an RA field according to a detected PDCCH DCI format.The RA field of each PDCCH includes two parts, an RA header field andactual RB allocation information. PDCCH DCI format 1, PDCCH DCI format2, and PDCCH DCI format 2A are the same in format for RA of type 0 andtype 1, and distinguished from one another by their 1 -bit RA headerfields according to a downlink system band. Specifically, type-0 RA andtype-1 RA are indicated by 0 and 1, respectively. While PDCCH DCI format1, PDCCH DCI format 2, and PDCCH DCI format 2A are used for type-0 RA ortype-1 RA, PDCCH DCI format 1A, PDCCH DCI format 1B, PDCCH DCI format1C, and PDCCH DCI format 1D are used for type-2 RA. A PDCCH DCI formatfor type-2 RA does not have an RA header field. Resource allocationfield indicates a PRB set of 1st slot. As will be explained below, incase of resource allocation type 0, 1, 2-LVRB, since there is no slothopping between 1st slot and 2nd slot, the same PRB set is allocated in2nd slot as allocated in 1^(st) slot (i.e., PRB index (1st slot)=PRBindex (2nd slot). Meanwhile, in case of resource allocation type 2-DVRB,if a PRB set of 1st slot is given, a PRB set of 2nd slot is determinedusing a slot hopping rule.

Referring to FIG. 7, in RA of type 0, RB allocation information includesa bitmap indicating RBGs allocated to a scheduled UE. An RBG is a set ofconsecutive PRBs. The size of an RBG, P depends on a system bandwidth asillustrated in Table 3 below.

TABLE 3 System Bandwidth RBG Size N_(RB) ^(DL) (P) ≦10 1 11-26 2 27-63 3 64-110 4

The total number of RBGs, N_(RBG) for a downlink system bandwidth ofN_(RB) ^(DL) PRBs is given by N_(RBG)=┌N_(RB) ^(DL)/P┘. Each of the└N_(RB) ^(DL)/P┘ RBGs is of size P and if N_(RB) ^(DL) mod P>0, one ofthe RBGs has a size of N_(RB) ^(DL)−P·└N_(RB) ^(DL)/P┘. Herein, modrepresents a modulo operation, ┌ ┐ represents a ceiling function, and └┘ represents a flooring function. The size of the bitmap is N_(RBG) andeach bit of the bitmap corresponds to one RBG. The RBGs are indexed from0 to N_(RBG)−1 in an ascending order of frequency. RBG 0 to RBGN_(RBG)−1 are sequentially mapped to the Most Significant Bit (MSB) tothe Least Significant Bit (LSB) of the bitmap.

Referring to FIG. 8, in RA of type 1, RB allocation information of sizeN_(RBG) indicates resources of an RBG subset on a PRB basis to ascheduled UE. An RBG subset p (0≦p<P) includes every P^(th) RBG,starting from RBG p. The RB allocation information has three fields. Thefirst field with ┌log₂(P)┘ indicates an RBG subset selected from among PRBG subsets. The second field with one bit indicates a shift of aresource allocation span within the RGB subset. If the bit value is 1,this means that the shift is triggered and if the bit is 0, this meansthat the shift is not triggered. The third field includes a bitmap inwhich each bit addresses a single PRB in the selected RBG subset. Thepart of the bitmap used to address PRBs in the selected RBG subset hassize N_(RB) ^(TYPE1) and is defined asN _(RB) ^(TYPE1) =┌N _(RB) ^(DL) /P┘−┌log₂(P)┘−1  [Equation 2]

The addressable PRB numbers of the selected RBG subset start from anoffset, Δ_(shift)(p) to the smallest PRB number within the selected RBGsubset, which is mapped to the MSB of the bitmap. The offset isexpressed as the number of PRBs and applied within the selected RBGsubset. If the bit value of the second field for shift of a resourceallocation span is set to 0, the offset for the RGB subset p is given byΔ_(shift)(p)=0. Otherwise, the offset for the RGB subset p is given byΔ_(shift)(p)=N_(RB) ^(RBGsubset)(p)−N_(RB) ^(TYPE1). N_(RB)^(RBGsubset)(o) is the number of PRBs in the RGB subset p and iscomputed by

$\begin{matrix}{{N_{RB}^{{RBG}\mspace{14mu}{subset}}(p)} = \{ \begin{matrix}{{{\lfloor \frac{N_{RB}^{DL} - 1}{P^{2}} \rfloor \cdot P} + P},} & {p < {\lfloor \frac{N_{RB}^{DL} - 1}{P} \rfloor{mod}\mspace{14mu} P}} \\{{{\lfloor \frac{N_{RB}^{DL} - 1}{P^{2}} \rfloor \cdot P} + {( {N_{RB}^{DL} - 1} ){mod}\mspace{11mu} P} + 1},} & {p = {\lfloor \frac{N_{RB}^{DL} - 1}{P} \rfloor{mod}\mspace{14mu} P}} \\{{\lfloor \frac{N_{RB}^{DL} - 1}{P^{2}} \rfloor \cdot P},} & {p > {\lfloor \frac{N_{RB}^{DL} - 1}{P} \rfloor{mod}\mspace{14mu} P}}\end{matrix} } & \lbrack {{Equation}\mspace{14mu} 3} \rbrack\end{matrix}$

Referring to FIG. 9, in RA of type 2, RB allocation informationindicates a set of contiguously allocated LVRBs or DVRBs to a scheduledUE. In case of RA signaled in PDCCH DCI format 1A, 1B or 1D, a 1-bitflag indicates whether LVRBs or DVRBs are allocated. For instance, ifthe flag is set to 0, this indicates LVRB allocation and if the flag isset to 1, this indicates DVRB allocation. On the other hand, if RA issignaled in PDCCH DCI format 1C, DVRBs are always allocated. A type-2 RAfield includes a Resource Indication Value (RIV), wherein the RIV iscorresponding to a start resource block RB_(start) and a length. Thelength represents the number of virtually contiguously allocated RBs.

FIG. 10 illustrates a wireless communication system having relays. Arelay or Relay Node (RN) extends the service area of a BS or isinstalled in a shadowing area to thereby provide a reliable service.Referring to FIG. 10, the wireless communication system includes a BS,relays, and UEs. The UEs communicate with the BS or the relays. For thesake of convenience, a UE communicating with a BS is referred to as amacro UE and a UE communicating with a relay is referred to as a relayUE. A communication link between a BS and a macro UE and a communicationlink between a relay and a relay UE are referred to as a macro accesslink and a relay access link, respectively. A communication link betweena BS and a relay is referred to as a backhaul link.

Relays are classified into L1 relays, L2 relays, and L3 relays accordingto their functionalities in multi-hop transmission. An L1 relay usuallyfunctions as a repeater. Thus, the L1 relay simply amplifies a signalreceived from a BS or a UE and transmits the amplified signal to the UEor the BS. Because the L1 relay does not decode a received signal, thetransmission delay of the signal is short. Despite this benefit, noiseis also amplified because the L1 relay does not separate the signal fromthe noise. To avert this problem, an advanced repeater or smart repeatercapable of UL power control or self-interference cancellation may beused. The operation of an L2 relay may be depicted asdecode-and-forward. The L2 relay can transmit user-plane traffic to L2.While the L2 relay does not amplify noise, decoding increasestransmission delay. An L3 relay whose operation is depicted asself-backhauling can transmit an Internet Protocol (IP) packet to L3. Asit is equipped with a Radio Resource Control (RRC) function, the L3layer serves as a small-size BS.

L1 and L2 relays may be regarded as part of a donor cell covered by aBS. In the case where a relay is part of a donor cell, the relay doesnot have a cell ID of its own cell ID because it cannot control its celland UEs of the cell. Nonetheless, the relay may still have a relay ID.At least part of Radio Resource Management (RRM) is controlled by the BSto which the donor cell belongs, while parts of the RRM may be locatedin the relay. An L3 relay can control cells of its own. Then the L3relay may manage one or more cells and each of the cells may have aunique physical-layer cell ID. The L3 relay may have the same RRMmechanism as a BS. From the perspective of a UE, there is no differencebetween accessing a cell controlled by the L3 relay and accessing a cellcontrolled by a normal BS.

Relays may be classified as follows according to mobility.

-   -   Fixed RN: as is implied from its appellation, this type RN is        permanently fixed for use in a shadowing area or for coverage        extension. It may function as a simple repeater.    -   Nomadic RN: this type RN is temporarily installed when users are        rapidly increasing in number, or is movable within a building.    -   Mobile RN: this RN can be installed in a public transportation        vehicle such as a bus or the subway. The mobility of the RN        should be supported.

The following classifications can also be considered according to thelinks between relays and networks.

-   -   In-based connection: a network-to-relay link shares the same        frequency band with a network-to-UE link in a donor cell.    -   Out-band connection: a network-to-relay link and a network-to-UE        link use different frequency bands in a donor cell.

With respect to the knowledge of the existence of a relay in a UE,relays are classified into the followings.

-   -   Transparent relay: a UE is not aware of whether or not it is        communicating with a network via the relay.    -   Non-transparent relay: a UE is aware of whether or not it is        communicating with a network via the relay.

FIG. 11 illustrates backhaul transmission in a Multicast BroadcastSingle Frequency Network (MBSFN) subframe. For in-band relaying, aBS-to-relay link (i.e. a backhaul link) operates in the same frequencyband as a relay-to-UE link (i.e. a relay access link). In the case wherea relay transmits a signal to a UE while it is receiving a signal from aBS or vice versa, the transmitter and receiver of the relay interferemutually. Accordingly, simultaneous BS-to-relay and relay-to-UEtransmissions on the same frequency resources may be limited. For thispurpose, the backhaul link and the relay access link are partitioned inTime Division Multiplexing (TDM). In an LTE-A system, a backhaul link isestablished in a subframe signaled as an MBSFN subframe to supportmeasurements of legacy LTE UEs located in a relay zone (fake MBSFN). Ifa subframe is signaled as an MBSFN subframe, a UE receives only thecontrol region of the subframe and thus the relay may configure abackhaul link using the data region of the subframe. Specifically, theMBSFN subframe is used for BS-to-relay transmission (e.g. a Relay PDCCH(R-PDCCH) and a Relay PDSCH (R-PDSCH), starting from the third OFDMsymbol of the MBSFN subframe.

Now, a description will be given of a method for allocating and managingresources for an R-PDCCH and an R-PDSCH according to embodiments of thepresent invention.

An R-PDCCH delivers DCI to a relay. For details of DCI, refer toTable 1. For example, the R-PDCCH may carry downlink schedulinginformation and uplink scheduling information to the relay. Downlinkdata for a relay (e.g. backhaul data) is received on an R-PDSCH. Acommunication procedure on the R-PDCCH and R-PDSCH is performed in thesame manner as or in a similar manner to step S102 of FIG. 1. That is,the relay receives an R-PDCCH and receives data/control information onan R-PDSCH indicated by the R-PDCCH. R-PDCCH transmission processing(e.g. channel coding, interleaving, multiplexing, etc.) may be carriedout in the same manner as defined by LTE or in a simplified manner ofthat defined by LTE, when needed. For instance, the R-PDCCH transmissionprocessing may be simplified in view of the nature of relays so that anunnecessary process as used in LTE is omitted.

The relay demodulates the R-PDSCH based on control information acquiredfrom the R-PDCCH. Therefore, it is very important to acquire informationabout the R-PDCCH accurately. In the legacy LTE system, a PDCCHcandidate region (i.e. a PDCCH search space) is reserved in a controlregion and a PDCCH is transmitted to a specific UE in a part of thePDCCH candidate region. Accordingly, the UE acquires its PDCCH from thePDCCH search space through blind decoding. Similarly, an R-PDCCH may betransmitted to a relay in the whole or part of reserved resources.

FIG. 12 is a diagram illustrating a signal flow for allocating resourcesfor an R-PDCCH and receiving the R-PDCCH using the allocated resourcesaccording to an embodiment of the present invention.

Referring to FIG. 12, a BS transmits R-PDCCH RA information to RNs(S1210). The R-PDCCH RA information is used to reserve an R-PDCCHresource area. Specifically, the R-RPDCCH RA information indicates thepositions of resources in which an R-PDCCH is likely to be transmittedto the RNs (a R-PDCCH search space configuration) in advance. For thesake of convenience, the signaling for reserving R-PDCCH resources instep S1210 will be referred to Signal #1. Signal #1 may be transmittedthrough higher layer signaling such as RRC signaling, MAC signaling,etc., preferably RRC signaling. In addition, Signal #1 may betransmitted in a semi-static manner. Signal #1 may be cell-specific,relay group-specific, or relay-specific.

The R-PDCCH search space refers to R-PDCCH resources (or an R-PDCCHresource area) that an RN is supposed to monitor to receive its ownR-PDCCH. The R-PDCCH search space includes a relay-common (RN-common)search space and/or a relay-specific (RN-specific) search space. A basicunit of the R-PDCCH resources may be an RB (e.g. 12 consecutivesubcarriers×7(6) consecutive OFDM symbols), a Resource Element Group(REG) (e.g. 4 available subcarriers×1 OFDM symbol), or a Control ChannelElement (CCE) (e.g. a plurality of (for example, 9) REGs).

The R-PDCCH resources (i.e. the R-PDCCH search space) reserved by Signal#1 are wholly or partially used for a later actual transmission of anR-PDCCH. In most cases, only a part of the reserved R-PDCCH resources isused for R-PDCCH transmission. Meanwhile, an RN should share resourceswith a macro UE in the data region of a backhaul subframe (e.g. an MBSFNsubframe). Therefore, it is preferred that the conventional LVRB/DVRBmapping rules are still applied to an RN like a macro UE, therebymaximizing the multiplexing efficiency of a frame. In this context,Signal #1 is configured based on the same signaling information as anLTE RA signaling configuration in order to reserve R-PDCCH resources(e.g. R-PDCCH RBs). Specifically, Signal #1 may provide VRB mappingscheme/allocation information. For example, Signal #1 may providevarious VRB mapping scheme/allocation information illustrated in FIGS. 6to 9. Preferably, Signal #1 may include information about contiguousVRBs (e.g. the start and length of the VRBs), as is done in DVRBallocation (refer to FIG. 9). Bit configuration in Signal #1 can use aformat of resource allocation types 0, 1 and 2 used in the conventionalLTE without modification, or use N bits bitmap when N VRBs are reservedfor R-PDCCH in advance. VRB to PRB mapping can be carried out inaccordance with resource allocation types 0, 1 and 2 of the conventionalLTE. In particular, with the resource allocation types 0, 1 and 2-LVRB,VRB indexes are mapped to PRB indexes of same value, and with resourceallocation type 2-DVRB, VRB indexes are distributed mapped to PRBindexes. The number of R-PDCCH RBs reserved by Signal #1 is not limitedto but is preferably a multiple of 4. Benefits that can be achieved fromthe number of R-PDCCH RBs being a multiple of will be described later. Agranularity for R-PDCCH resource allocation may be one RB, one RBG, or agroup of X RBs (e.g. a group of 4 RBs), when needed. Preferably, theR-PDCCH resource allocation granularity is 4 RBs or a multiple of 4 RBs,which will be detailed later.

In the legacy LTE system, VRB allocation information (e.g. DVRB RAmapping signaling information) is transmitted only to one LTE UE.However, RA information (Signal #1) having the same configuration as ora similar configuration to the conventional VRB allocation information(e.g. the conventional DVRB RA mapping signaling information) may betransmitted to a plurality of (e.g. all) RNs and the RNs may determinethe positions of R-PDCCH resources according to a conventional LTE RArule (e.g. a DVRB interleaving rule) in an embodiment of the presentinvention (RN (group) common signaling). While not shown, Signal #1 maybe transmitted only to one RN, as is conventionally done in the legacyLTE system (RN dedicated signaling).

When Signal #1 is transmitted through higher layer signaling on anR-PDSCH, there is no way for an RN to know a reserved resource area foran R-PDCCH during an initial access. Accordingly, the RN may assume theexistence of an R-PDCCH in an RB with a specific RB index and decode theR-PDCCH during the initial access (a UE mode). Then, the RN maydetermine a resource area reserved for an R-PDCCH from Signal #1received through higher layer signaling (e.g. RRC signaling) in asemi-static manner (an RN mode). However, if the reserved R-PDCCH areahas been changed, the RN may not know the exact time when the reservedR-PDCCH has been changed. As a result, R-PDCCH decoding may bedefective. Even though there is no problem with R-PDCCH decoding, the RNmay have to attempt decoding to detect an R-PDCCH in many cases. Tominimize this problem, the size of the reserved R-PDCCH area may beincreased or decreased by one basic unit each time it is changed.Obviously, this information should be considered in determining thepositions and number of R-PDCCH RBs included in semi-static RRCsignaling. For instance, the reserved R-PDCCH area may be increased ordecreased in size by a multiple of 4 RBs. In this case, the RN has todetect an R-PDCCH in an extra R-PDCCH area as well as an existingR-PDCCH area or in a decreased R-PDCCH area as well as the existingR-PDCCH area in the vicinity of a subframe having a changed R-PDCCH area(i.e. before or after the subframe), for example, after receiving RRCsignaling. In this manner, decoding complexity caused by an arbitraryR-PDCCH RB configuration can be reduced.

Meanwhile, if the RN is capable of directly receiving an R-PDCCH, Signal#1 may be transmitted in DCI of an R-PDCCH (for example, in the casewhere a subframe boundary is a few symbols misaligned between the BS andthe RN and thus the RN can receive an R-PDCCH directly). In this case,the RN can determine a resource area reserved for an R-PDCCH on asubframe basis.

Referring to FIG. 12 again, the BS transmits R-PDCCHs in a backhaulsubframe (S1220). The R-PDCCHs may be transmitted in the whole or partof the R-PDCCH resources reserved by Signal #1 in step S1210. In mostcases, only a part of M R-PDCCH RBs are used for R-PDCCH transmission.DCI mapped to R-PDCCH resources (e.g. R-PDCCH RBs), such as a DL grant(downlink scheduling information) and a UL grant (uplink schedulinginformation), may not be cross-interleaved. In this case, only a singleR-PDCCH is transmitted in one or more RBs. The DCI mapped to the R-PDCCHresources may also be intra-RB interleaved. The DCI mapped to theR-PDCCH resources may also be inter-RB interleaved (cross-interleaved).In this case, a plurality of R-PDCCHs may be transmitted together in oneor more RBs. Subsequently, each RN monitors the R-PDCCH resources (theR-PDCCH resource area) reserved by Signal #1 received in step S1210 todetermine whether there is any R-PDCCH destined for the RN. Monitoringthe R-PDCCH resources involves blind decoding of R-PDCCH candidates.Upon detection of its own R-PDCCH, an RN performs an operation accordingto the DCI of the R-PDCCH (e.g. downlink reception, uplink transmission,etc.).

It is regulated that an R-PDCCH carrying a DL grant (referred to as a DLgrant R-PDCCH) is transmitted in the first slot of a subframe and anR-PDCCH carrying a UL grant (referred to as a UL grant R-PDCCH) istransmitted in the second slot of the subframe. Thus, if a DL grantR-PDCCH exists only in the first slot, the second slot may be wasted.Accordingly, an R-PDCCH is preferably transmitted in the second slot. Inthis regard, an R-PDSCH resource area allocated to a specific RN may beoverlapped with an R-PDCCH resource area reserved for R-PDCCHs, forexample, by RRC signaling. In this case, an RN (or a procedure) may beconfigured so as to acquire an R-PDSCH only from the second slot, for anoverlapped RB. To increase resource utilization, an RN (or a procedure)may be configured such that an R-PDSCH is demodulated in the secondslot, only for an RB carrying an R-PDCCH, and also in the first slot foran RB that does not carry an R-PDCCH. In this manner, the RN candetermine the existence of a first R-PDCCH area and acquire an R-PDSCHfrom the remaining area, while still using conventional LTE RA, whichwill be described again.

The present invention provides a method for allocating resources for aRelay-Physical Downlink Control Channel (R-PDCCH) transmitted from a BSto an RN and managing the allocated resources (e.g. RA Type 2). Every RNcan demodulate an R-PDSCH based on control information acquired from itsR-PDCCH. Accordingly, it is very important to acquire accurate R-PDCCHinformation. In the legacy LTE system, a resource area for transmittinga PDCCH is reserved in advance and a PDCCH is transmitted to a specificUE in a part of the reserved PDCCH resource area. The reserved PDCCHarea is referred to as a Search Space (SS) and a UE acquires its PDCCHby blind decoding in the SS.

According to the present invention, an R-PDCCH is transmitted to aspecific RN in all or a part of M R-PDCCH RBs reserved for transmittingcontrol information needed for R-PDSCH demodulation. Information aboutthe reserved M R-PDCCH RBs may be indicated by RRC signaling orbroadcast on a PBCH. An R-PDCCH SS may be configured cell-specificallyor RN-specifically. After the R-PDCCH SS is configured, it may bechanged semi-statically by RRC signaling.

The whole area in which R-PDCCHs are likely to be located may be presetor indicated by RRC signaling. An area carrying an actual R-PDCCH or acertain area including this R-PDCCH area (e.g. RN-specific SS≦the wholearea) may also be indicated by higher-layer signaling (e.g. RRCsignaling). Information about the limited SS transmitted to an RN may beused in determining an interleaver parameter, for example, aninterleaver size for an R-PDCCH. This implies that the informationtransmitted to the RN may determine the characteristics of aninterleaver for the R-PDCCH. Especially, the same information may betransmitted to a plurality of RNs (e.g. RNs within the same interleavinggroup) and R-PDCCH RBs allocated to these RNs may be jointlyinterleaved. The number of R-PDCCH RBs allocated to the RNs may alsodetermine the characteristics of an interleaver used for R-PDCCHs. Inaddition, information about a limited SS may limit the number of RNsthat are subject to joint interleaving (i.e. the number of RNs in thesame interleaving group). The information about the limited SS may beused in limiting the number of RBs to which interleaved R-PDCCHs aremapped. That is, as only R-PDCCHs for a predetermined number of RNs areinterleaved to limited or predetermined RBs, an interleaver of apredetermined size can be used. For example, if two RNs are allocated to4 RBs, only an interleaver having an interleaver size of 4 RBs may bedesigned. While an interleaver size of 8 RBs or 2 RBs may also besupported to increase interleaving freedom, an interleaver with alimited interleaver size in RBs is preferable due to the resultingincreased complexity in interleaver design. For example, for 4 or 8 RBs,2 or 4 RBs may be interleaved. In this case, only two interleaver sizesare sufficient, which obviates the need for supporting all interleavertypes and interleaver sizes and thus simplifies interleaverimplementation.

FIG. 13 illustrates an example of R-PDCCH interleaving using only twotypes of interleavers.

In the illustrated case of FIG. 13, R-PDCCHs are interleaved in twointerleavers of different sizes. A BS may group R-PDCCHs for RN 1 and RN2 into interleaving group #1 and interleave interleaving group #1according to interleaver size A. The BS may also group R-PDCCHs for RN 3and RN 4 into interleaving group #2 and interleave interleaving group #2according to interleaver size A. Meanwhile, the BS may interleave anR-PDCCH for RN5 as a single interleaving group according to interleaversize B. While the BS interleaves R-PDCCHs and maps them to consecutiveRBs in FIG. 13, by way of example, the interleaved R-PDCCHs may bemapped to distributed RBs in actual implementation.

With reference to FIGS. 14 to 18, methods for multiplexing R-PDCCHs withR-PDSCHs in resources allocated according to a DVRB scheme. For the sakeof convenience, the R-PDCCHs and the R-PDSCHs are shown as transmittedin the first slot and in the first/second slot, respectively. However,the R-PDCCH and R-PDSCH transmission is exemplary. For instance, theR-PDCCHs may be transmitted on a slot basis in the first and/or secondslot. In LTE-A, a DL grant R-PDCCH and a UL grant R-PDCCH aretransmitted in the first and second slots, respectively. Unlessotherwise specified, an RB may refer to a VRB or a PRB undercircumstances.

FIG. 14 illustrates a method for multiplexing R-PDCCHs with R-PDSCHs in24 DVRBs, for four RNs. The four RNs may be a preset RN group scheduledto use the 24 allocated R-PDCCH RBs. That is, the illustrated R-PDCCHRBs may be dedicated to the RNs (or the RN group). Because slot-basedcyclic shift (DVRB slot hopping) is adopted in the DVRB scheme, one RNis not allowed to use two slots of the same PRB. That is, an R-PDCCH(and an R-PDSCH) is not transmitted to an RN in the two slots of thesame PRB. If the R-PDCCH/R-PDSCH is demodulated using aDeModulation-Reference Signal (DM-RS), the resulting degraded channelestimation performance leads to the degradation of demodulationperformance. Considering that an R-PDCCH is transmitted in a goodchannel environment in most cases, it is preferred to allocate the twoslots of the same PRB to the same RN (i.e. an R-PDCCH (and an R-PDSCH)).For this purpose, DVRB slot hopping may not be applied in DVRB-basedR-PDCCH RA. Resources for an RN are allocated to the same VRB set in thefirst and second slots. The slot hopping-off may apply to all DVRBresources allocated by Signal #1 or to actual resources carryingR-PDCCHs.

As illustrated in FIG. 14, a basic VRB grouping unit for allocatingDVRBs to an RN is a multiple of 4, VRB #0 to #3, VRB #4 to #7, VRB #12to #15, or VRB #16 to #19 in an embodiment of the present invention.Resources for an RN are allocated to the same VRB set in the first andsecond slots. In spite of DVRB slot hopping, the same PRBs in two slotsmay be allocated to the same RN. That is, the same PRBs of two slots areavailable to transmission of an R-PDCCH (and an R-PDSCH) to the same RNthrough DVRB allocation.

Therefore, a basic resource allocation unit for an RN may be 4. Forinstance, 4 RBs may be a resource allocation unit for an RN in asituation where backhaul resources are allocated in both a distributedmanner and a localized manner. Hence, a multiple of 4 RBs can beallocated to an RN. In this case, the number of bits required for an RAfield may be reduced using an RB step (e.g. step=4). In addition, eventhough four RBs (e.g. VRB #0 to #3) are cyclically shifted in the secondslot, each of the cyclically shifted RBs is adjacent to one of the fourRBs in the first slot. Therefore, even though slot hopping is off onlyfor M RBs (e.g. an R-PDCCH search space) reserved for R-PDCCHtransmission, the M RBs do not interfere with other RBs to which slothopping is applied. For the last VRB index, two VRBs may be paired, notfour VRBs. Similarly to the above manner, resources for transmission ofan R-PDCCH can be allocated to RN #1, RN #2 and RN #3.

FIG. 15 illustrates another method for multiplexing R-PDCCHs withR-PDSCHs in resources allocated according to the DVRB scheme. Resourcesof a DVRB resource area assumed in FIG. 13 are allocated to an RN thatdoes not belong to the RN group of FIG. 13. In this manner, resourcesallocated to the RN group can be efficiently utilized.

Referring to FIG. 14 again, an R-PDCCH for RN #4 is not interleaved inthe R-PDCCH area (for RN #0 to RN#3) and thus RN #4 is from another RNgroup. Let RN #0 to RN#3 form RN Group #1. Then the resources (orresource area) of FIG. 13 are intended for RN Group #1. In this example,even though RN #4 is from another RN group, resources may be allocatedto RN #4 for an R-PDCCH and/or an R-PDSCH in the resources of RN Group#1, thereby increasing resource use efficiency, as illustrated in FIG.15. In this case, information indicating that the resources (area) areallocated to another RN (RN group) should be transmitted together withor separately from RA signaling information. In an embodiment of thepresent invention, a signal indicating an RN or an RN group (a GroupIndication Signal (GIS)) may be transmitted. That is, the GIS and a DVRBsignal may be used in allocating resources. The GIS may be inserted inan RA field or carried in a separate field. If the GIS does not changeoften, the GIS may be indicated by higher layer signaling (e.g. RRCsignaling or MAC signaling).

FIG. 16 illustrates a third method for multiplexing R-PDCCHs withR-PDSCHs in resources allocated according to the DVRB scheme. Thismethod maximizes resource use efficiency by modifying a conventional RA.

Referring to FIG. 16, if RN #0 is paired with RN #1 and 4 RBs areconfigured for them, a common DVRB signal (PRB #0/6=VRB#0/1/2/3) may betransmitted to RN #0 and RN #1 to notify them of the allocated resourcearea and to instruct them not to follow LTE PDSCH DVRB mapping in thesecond slot. That is, the DVRB signal may be reconfigured so that thefirst and second slots of the same RB index are used without slot-basedshifting. According to the conventional DVRB mapping rule, RB #0 in thefirst slot is cyclically shifted to RB #12 in the second slot accordingto a gap value. However, the cyclic shift may degrade channel estimationperformance and thus demodulation performance, when an R-PDCCH/R-PDSCHis demodulated using a DM-RS.

Therefore, an RN may use the same RBs in the first and second slotwithout RB shifting in the second slot. For this operation, additionalsignaling may not be needed. A conventional operation mode and aproposed operation mode may be configured together. For example,shifting-off (i.e. slot hopping-off) is applicable only to RBs to whichR-PDCCHs are actually allocated. Alternatively, shifting-off may beapplied to all RBs of an R-PDCCH search space. For an R-PDSCH,shifting-off is applicable only when resources carrying an R-PDCCH areoverlapped with resources indicated by the R-PDCCH. In addition,shifting-off is applicable only to RBs to which R-PDSCHs are actuallyallocated. Shifting-off may also be applicable to all RBs available toan RN in a backhaul subframe.

FIG. 17 illustrates a fourth method for multiplexing R-PDCCHs withR-PDSCHs in resources allocated according to the DVRB scheme.

Referring to FIG. 17, an R-PDCCH resource area is known to RNs and eachRN monitors an R-PDCCH candidate area (i.e. an R-PDCCH search space) todetect its own R-PDCCH. In this method, an RN to use the second slot isdetermined according to the index of a Relay CCE (R-CCE) to which anR-PDCCH is allocated for RN #k (k=0, 1, 2, 3). For example, this methodmay be carried out based on an R-CCE-index to RB-index mapping rulewhich is not restricted to a specific one. For example, the second slotof an RB carrying an R-PDCCH may be mapped to an RN corresponding to theR-PDCCH. To be more specific, if an R-CCE for an R-PDCCH of RN #0 ismapped to RB #0, an R-CCE for an R-PDCCH of RN #1 is mapped to RB #6, anR-CCE for an R-PDCCH of RN #2 is mapped to RB #12, and an R-CCE for anR-PDCCH of RN #3 is mapped to RB #18, the second slots of RB #0, 6, 12and 18 may be mapped to RN #0, 1, 2, and 3, respectively. Thus, R-PDSCHsand R-PDCCHs are allocated as illustrated in FIG. 17.

According to the above description, it is possible to allocate theresources of the second slot of an RB carrying an R-PDCCH for an RN tothe RN (e.g. for an R-PDSCH) without additional signaling (implicitsignaling). The remaining RBs carrying R-PDSCHs may be allocated to RNsby RA included in R-PDCCHs. In this case, an RN may be configured so asto demodulate an R-PDSCH by distinguishing RBs carrying R-PDCCHs fromRBs that does not carry R-PDCCHs. For this purpose, the first slot ofall RBs (an R-PDCCH search space) reserved for R-PDCCHs may be excludedfrom R-PDSCH transmission (or R-PDSCH demodulation). In another method,an RN may exclude only the first slot of an RB from which its ownR-PDCCH (it may be restricted to a DL grant R-PDCCH) is detected fromR-PDSCH transmission (or R-PDSCH demodulation). Specifically, when theRN detects at least part of a DL grant R-PDCCH in the first slot of aPRB, the RN may exclude the first slot of the PRB in R-PDSCHdemodulation. In a further method, an RB carrying an R-PDCCH may beindicated explicitly.

FIG. 18 illustrates an extension of FIG. 17. Therefore, it is assumedthat the second slot of an RB carrying an R-PDCCH is implicitly mappedto an RN corresponding to the R-PDCCH as in FIG. 17. In this case, ifthere are a small number of RBs carrying R-PDCCHs due to a small numberof RNs, some RBs may not be allocated in the second slot, thus wastingresources. This resource waste may be prevented by increasing a CCEaggregation level. Referring to FIG. 18, if there are only R-PDCCHs fortwo RNs in an R-PDCCH resource area (e.g. 4 RBs), the R-PDCCHs of thetwo RNs may be transmitted over the four RBs by increasing an R-PDCCHR-CCE aggregation level. For this purpose, a CCE-to-RB mapping rule maybe used. The CCE-to-RB mapping rule is not limited to a specific one.For instance, R-CCE #0 may be mapped to RB #0, R-CCE #1 may be mapped toRB #6, R-CCE #2 may be mapped to RB #12, and R-CCE #3 may be mapped toRB #18. On the assumption of four R-CCEs for four RBs (i.e. one R-CCEper RB), R-CCE #0 and #1 may be mapped to RN #0 and R-CCE #2 and #3 maybe mapped to RN #1 (a CCE aggregation level=2). Thus an R-PDSCH for anRN may be allocated implicitly so as to include one or more R-PDCCHtransmission areas. In the illustrated case of FIG. 18, the second slotsof RB#0 and RB#6 are implicitly allocated to RN #0 (for an R-PDSCH), andthe second slots of RB#12 and RB#18 are implicitly allocated to RN #1(for an R-PDSCH).

FIG. 19 illustrates an example of transmitting R-PDCCHs and R-PDSCHsaccording to the above-described method.

In FIG. 19, it is assumed that there are 18 RBs (or RBGs) in total and atotal SS is composed of RBs (or RBGs) #0, #3, #5, #6, #8, #11, #14 and#17 out of the 18 RBs (or RBGs). It is also assumed that R-PDCCHs aretransmitted only in RBs (or RBGs) #0, #3, #5, #6, #8 and #11 in aspecific subframe. For R-PDCCH reception, RN 1 and RN 2 are supposed todecode RBs #0, #3 and #6, and RN 3 and RN 4 are supposed to decode RBs#5, #8 and #11 in the illustrated case of FIG. 19. The number of RBsthat an RN should search may be indicated by RN-specific signaling.

Referring to FIG. 19, RN 1 and RN 2 assume that their R-PDCCHs may existin RBs (RBGs) #0, #3 and #6 in the first slot of the subframe. Based onthis assumption, RN 1 and RN 2 may decode R-PDSCHs successfully in thesecond slot of the subframe and other RBs (RBGs). Further, if RN 1 andRN 2 can also be aware of areas carrying R-PDCCHs to RN 3 and RN 4, thatis, RBs (or RBGs) #5, #8 and #11, RN 1 and RN 2 determine that R-PDCCHsmay exist in the first slots of RBs (or RBGs) #5, #8 and #11 as well asin the first slots of RBs (or RBGs) #0, #3 and #6 in the subframe. Thus,the BS may allocate R-PDSCHs only to the second slots of the RBs (orRBGs) carrying the R-PDCCHs or leave the second slots of the RBs (orRBGs) carrying the R-PDCCHs empty. It may be also assumed that the otherRBs (or RBGs) #10, #12, #13, #14, #15, #16 and #17 can carry R-PDSCHs toRN 1 and RN 2, starting from their first slots, if the R-PDSCHs arescheduled for RN 1 and RN 2.

Therefore, if an R-PDSCH is allocated to a PRB other than PRBs carryingR-PDCCHs, the R-PDSCH may be transmitted, starting from the first slotof the allocated PRB. On the other hand, an R-PDSCH is allocated to thesecond slot of a PRB pair that carries an R-PDCCH in its first slot.

For RN 1 and RN 2 to identify PRBs whose first slots are not availablefor R-PDSCH transmission, the BS may signal actual PRBs carryingR-PDCCHs of group #1 and group #2. In addition, the scheduler should notallocate R-PDSCHs for RNs of group #1 to PRBs carrying R-PDCCHs forgroup #2 (in their first slots). Instead, the scheduler should transmitR-PDSCHs, starting from the first slot, in PRBs other than PRBs carryingR-PDCCHs for the RNs of group #1 and group #2. RN decoding is also basedon this assumption.

Therefore, an RN performs R-PDSCH decoding in a PRB pair, starting withthe first slot, if the PRB pair does not carry an R-PDCCH. On thecontrary, if the PRB pair carries an R-PDCCH, the RN does not attemptR-PDSCH decoding in the first slot of the PRB pair. This operation maybe performed based on blind decoding, instead of signaling. Tofacilitate blind decoding, a unit (e.g. the number of RBs) in which theRN attempts decoding may be limited. For instance, if the RN fails todetect an R-PDCCH by blind decoding in one (e.g. 25 RBs) of candidateunits, it may attempt blind decoding in a blind decoding RB area of thenext size (e.g. 50 RBs). If the RN succeeds in the blind decoding, itmay determine that an R-PDCCH exists in the RBs. In this case, the RNmay assume that at least its R-PDCCH is not present in the other RBs,while it does not know whether any R-PDCCH exists in the other RBs. Inaddition, the RN assumes that its R-PDSCH exists in an RB or RBGindicated by RA information. Accordingly, the RN may perform R-PDSCHdecoding, determining that an R-PDCCH may exist in the first slot of anR-PDCCH-detected SS. Meanwhile, if an RA bit (an RB or RBG allocationindicator) indicates the presence of data in an SS where an R-PDCCH hasnot been detected, the RN performs demodulation, determining that thefirst slot of the RB or the RBG does not have an R-PDCCH. In this case,the BS should allocate the data to an appropriate RB accordingly. Inanother method, an R-PDSCH for RN 1 of group #1 may be transmitted in anR-PDCCH area of group #2. It is natural on the part of RN 1 because RN 1does not know the existence of group #2. However, since the BS candetermine whether the R-PDSCH of RN 1 exists in the R-PDCCH area ofgroup #2, the BS may schedule in such a manner that the R-PDSCH of RN 1is not overlapped with R-PDCCHs of RN 3 and RN 4. Meanwhile, an RNdetermines the presence or absence of its R-PDCCH by blind decoding andperforms R-PDSCH decoding according to the determination.

In the mean time, the BS may indicate RBs carrying an R-PDCCH to eachRN. For example, the BS may indicate RBs carrying an R-PDCCH in theirfirst slots from among RBs carrying R-PDSCHs. However, since the numberof RBs that the BS should indicate to the RN is changed, a signalingformat used to indicate the RBs is also changed.

SS Design Based on Multi-Level Blind Decoding

FIGS. 20 and 21 illustrate an example of configuring R-PDCCH RBs.

Referring to FIGS. 20 and 21, RBs carrying an R-PDCCH to an RN may besignaled semi-statically by RRC signaling and the R-PDCCH may betransmitted actually in part of the RBs. An actual resource areacarrying an R-PDCCH may be identical to or different from anRRC-configured R-PDCCH area (an interleaving unit in most cases). In thelatter case, the actual resource area carrying the R-PDCCH may bedetermined by blind decoding. Specifically, M RBs are set as a candidateR-PDCCH transmission set and the R-PDCCH is transmitted in an N RBsubset (M≧N). Basically, a different subset may be set for each RN,while an R-PDCCH for one RN may be distributed across a plurality ofsubsets. The RN performs blind decoding on an aggregation level basiswithin the subset in order to receive an R-PDCCH. The problem is thatbecause the RN does not know the positions of R-PDCCHs for other RNs,the BS transmits data in the remaining area except all positions atwhich R-PDCCHs are likely to be transmitted in the above-describedcandidate set or on the assumption that predetermined areas of RBs orRBGs allocated to R-PDCCHs are available or unavailable for datatransmission. Herein, full interleaving or partial interleaving isapplicable.

Full interleaving refers to interleaving R-PDCCHs of all RNs accordingto an interleaving unit and then mapping the interleaved R-PDCCHs toPRBs, whereas partial interleaving refers to joint interleaving onlyR-PDCCHs of some RNs. On the part of an RN, if a single R-PDCCHinterleaving area is to be monitored, it may determine fullinterleaving. If a plurality of R-PDCCH interleaving areas are includedin a monitoring set, the RN may determine partial interleaving.Therefore, the terms may have different meanings on the parts of a BSand an RN.

However, it may often occur that after interleaving, an R-PDCCH of aspecific RN is not mapped uniformly to an R-PDCCH RB set in a total band(e.g. a system band) or a partial band. That is, if an interleaver unitis 4 REs (e.g. an REG), an R-PDCCH having 36 REs (e.g. 1 CCE) may bemapped uniformly to 9 RBs (4 REs per RB). However, if the R-PDCCH shouldbe mapped to 9 or more RBs, some RBs of the R-PDCCH subset may notinclude even a part (e.g. 4 REs) of the R-PDCCH of the RN. In this case,this R-PDCCH area cannot be used to deliver an R-PDSCH even though itdoes not include the R-PDCCH, like an R-PDCCH RB. That is, none of theRNs of an RN group subject to joint interleaving can use the RBs of anR-PDCCH subset in receiving an R-PDSCH.

To avoid this resource waste, the interleaving range (e.g. a band orRBs) of an RN group is set to match the amount of resources (e.g. thesize of a band or the number of RBs) that can be allocated or used forall RNs of the RN group after interleaving. While the two sizes may notbe perfectly equal, an extra band or extra RBs are preferably minimized.For instance, if four R-PDCCHs each having one RB should be transmittedto four RNs, the four R-PDCCHs may be mapped to four RBs afterinterleaving. In this case, four consecutive logical indexes may beassigned to the R-PDCCHs. However, four PRB indexes for the R-PDCCHs maybe apart from one another by a predetermined interval (e.g. 3 or 4 RBsas an RBG size unit). Herein, the interval is determined according to anRBG size. Thus, the R-PDCCH PRB indexes may be non-contiguous (e.g. 0,4, 8 . . . ). As a consequence, the four R-PDCCHs are transmitted across4 RBs. If 7 R-PDCCHs are to be transmitted to 7 RNs, each to one RN, butthe basic interleaving unit is a multiple of 4 RBs, a total of 8 RBs maybe reserved for the 7 R-PDCCHs. Then, resources corresponding to the REsof one RB may be wasted. Nonetheless, the proposed method can reduce theresource waste remarkably, compared to the afore-described method.Setting of the basic interleaving unit such as 4 serves the purpose ofreducing the number of blind decodings, as described later. Blinddecoding may be performed in two methods: one is to blind-decode 4 RBsand then blind-decode the next 4 RBs that do not overlap with theprevious 4 RBs and the other is to blind-decode RB #0 to RB #3 (4 RBs)and then blind-decode RB #0 to RB #7 (8 RBs).

On the assumption that 8 R-PDCCHs each having one CCE are transmitted to8 RNs, each R-PDCCH to one RN (one CCE corresponds to the number ofavailable REs in the first slot of a PRB pair, for example), a total of8 RBs are required and interleaving is performed on an 8-RB basis. Inthis scheme, the BS does not indicate a (partial) interleavingband/depth to the RNs. Instead, it is known to the BS and the RNs thatif a minimum interleaving unit is 4 RBs, the interleaving band/depth isdefined as a multiple of 4 RBs. Under this setting, each RN performsblind decoding on the minimum unit, that is, on 4 RBs (first-step blinddecoding). If the RN fails to detect an R-PDCCH, it may double theinterleaving band/depth to 8 RBs and thus perform blind decoding on 8RBs (second-step blind decoding). If the RN succeeds in blind decodingfor the interleaving band/depth, the RN completes the band/depth search.On the contrary, if the RN fails in blind decoding for the interleavingband/depth, the RN proceeds to the next R-PDCCH aggregation level searchstep. In this manner, R-PDCCHs are interleaved in units of a minimumrequired amount of resources and mapped to PRBs. Then each of the RNsperforms blind decoding on R-PDCCH resources with contiguous logicalindexes within a basic blind decoding range B1 (e.g. 4 CCEs) afterdeinterleaving. If the RN fails in the blind decoding, it performs blinddecoding in an increased bandwidth, that is, a widened blind decodingrange B2 (e.g. 8 CCEs). Thus, the RN can decode an R-PDCCH successfully.The blind decoding of the blind decoding ranges B1 and B2 is done todetermine an interleaving depth, not an aggregation level. The basicgranularity B1 may be set to various values such as 1, 2, 3, 4, . . .and the blind decoding range B2 may be given as a multiple of B1 or thesum of B1 and a predetermined value.

An interleaver row size may vary with the size of an R-PDCCH to betransmitted/interleaved. While it is preferred to keep an interleavercolumn size unchanged, it is possible to change the interleaver columnsize within a given number of columns sizes such as 8, 16, and 32. Theinterleaver column size may be indicated by higher-layer signaling.Since the granularity with which the interleaver band/depth is changedis larger than 1, as many interleavers as the number of RBs in a systemband are not required. For example, if an interleaving size granularityis 16 RBs in a 96-RB system, about 6 interleaver sizes may besufficient.

To reduce the number of interleavers to be designed, the followingmethod may further be contemplated. For example, if an interleaver sizeis 4 and R-PDCCHs are to be transmitted with a band/depth of 8 RBs, two4-RB interleavers may be concatenated. That is, since the R-PDCCH bandis 8 RBs, two 4-RB interleavers can be used. In this manner, a systemcan be implemented only with a single interleaver. As stated before, itis possible to change an interleaver row size, while fixing aninterleaver column size, or vice versa.

Importantly, the size of R-PDCCHs to be transmitted determines theactual transmission band/depth (e.g. 7 RBs) of the R-PDCCH. In thiscase, the BS selects the smallest interleaving band/depth (e.g. B1×2=8RBs) including 7 RBs and transmits the R-PDCCHs using the selectedinterleaving band/depth. On the other hand, an RN performs blinddecoding by increasing an interleaving band/depth or its index, startingfrom a basic interleaving band/depth, until an R-PDCCH is finallydetected. Another feature is to use a variable interleaver size.Alternatively or additionally, a basic interleaver size is defined andinterleavers each having the basic interleaver size are concatenated,for interleaving.

FIG. 22 illustrates a case where an interleaving depth is not applied.Each box is a logical representation of CCE resources in the first slot.A CCE may be defined as 9 REGs or available REs in the first slot of aPRB pair. Referring to FIG. 22, an R-PDCCH is mapped to one or more CCEsaccording to a CCE aggregation level.

FIG. 23 illustrates a case in which an interleaving depth is appliedaccording to the present invention.

Referring to FIG. 23, an RN performs blind decoding to determine aninterleaving depth. That is, the RN may perform blind decoding in blinddecoding ranges B1, B2, B4 and B8 sequentially until it detects anR-PDCCH. If the RN fails in blind decoding in the blind decoding rangesB1, B2, B4 and B8, the RN repeats the same operation for the nextaggregation level. On the assumption that the RN succeeds in blinddecoding of an R-PDCCH in the blind decoding range B2, the RN performsR-PDSCH demodulation, determining that an R-PDCCH exists in any RB ofB2. That is, the RN assumes that no R-PDSCH exists in any slot of theblind decoding range B2 including the first slot of an RB in which theR-PDCCH has been detected, for R-PDSCH demodulation. On the other hand,the RN does not assume the presence of an R-PDCCH outside the blinddecoding range B2. Therefore, the RN performs R-PDSCH demodulation inallocated RBs, considering that RBs indicated by the BS (the remainingarea) do not have an R-PDCCH. Obviously, an R-PDCCH may exist in theremaining area. However, as an R-PDSCH is allocated to an RB that doesnot carry an R-PDCCH, the RN can accurately demodulate the R-PDSCHwithout impairing the assumption set for RN R-PDSCH demodulation (i.e.the absence of an R-PDCCH in the first slot of the allocated RB).

FIG. 24 illustrates multi-level blind decoding.

Referring to FIG. 24, an RN performs blind decoding for interleavingdepth B1. If the RN fails in detecting an R-PDCCH based on interleavingdepth B1, the RN performs blind decoding for interleaving depth B2.Similarly, the RN increases the interleaving depth until it succeeds inblind decoding. While interleaving randomizes inter-cell interference,interference can be further mitigated by setting a different blinddecoding starting position for each cell. In FIG. 24, cells may differin a blind decoding starting position and a blind decoding depth Bi(i=1, 2, 3, . . . ). For example, there is no need for setting acell-specific blind decoding starting position in units of B1. A blinddecoding starting offset may set for a cell according to the level ofinterference. In case of a 3-cell structure, an offset may be set to asystem band/3. While Bi values are shown to widen a blind decoding areain one direction with respect to a starting point, the blind decodingarea may be extended in both directions from a starting index.Especially without interleaving, such an offset may minimizeinterference. If the same starting index is set for each cell, an offsetmay be applied to an interleaver for each cell. That is, an interleaveroffset may be set according to a cell ID or a cell-specific value so asto achieve a different interleaving result for each cell.

A change of an interleaver size amounts to a change of a row×columnvalue. If the number of columns is given, the number of rows may bechanged or vice versa. The interleaver size may be changed according tothe total number of REGs in a PRB to which an R-PDCCH is mapped. Forexample, on the assumption that each RB includes 8 REGs in the firstslot of a subframe and a total frequency band is 20 MHz (i.e. 100 RBs),there are 800 REGs in total (=8 REGs×100 RBs). Typically, all of theREGs are not defined as an SS. In this case, interleaved REG indexes areachieved by inputting 800 REG indexes to an interleaver with 32 columns,subjecting the REG indexes to column permutation, and reading thepermuted REG indexes column by column. If the number of REGs for an SSis reduced to 400, the indexes of the REGs may be interleaved byreducing the number of rows, while the number of columns is maintainedin the interleaver. In this sense, the interleaver may be referred to asa variable interleaver.

Meanwhile, if a UL grant SS is configured independently in the secondslot of the subframe, the above-described proposed method may also beapplied to the second slot.

FIG. 25 illustrates an example of mapping R-PDCCHs to PRBs. Morespecifically, FIG. 25 illustrates an operation for mapping logicalR-PDCCH indexes (e.g. CCE indexes, REG indexes, or interleaving unitindexes) to PRBs through an interleaver. Interleaving may be performedonly when needed. The R-PDCCH-to-PRB mapping is performed under thefollowing conditions.

-   -   Interleaver size (the following features are applicable to every        afore-described interleaver).        -   Only the column size is fixed, while the row size is            variable.            -   Or a few values may be available as the column size.            -   The column size may depend on a bandwidth.        -   Column permutation may be performed.    -   Interleaver On/Off        -   The interleaver may be used or not according to a            transmission mode/configuration.        -   The interleaver is basically off. The interleaver may be            activated or deactivated (on or off) by higher-layer            signaling.        -   For DM RSs, the interleaver is off all the time. For CRSs,            the interleaver is on all the time.

R-PDCCHs are mapped to PRBs at predetermined positions in an SS reservedfor R-PDCCH transmission (i.e. an R-PDCCH SS). If interleaving is off,an R-PDCCH is mapped in units of a basic unit (e.g. a CCE) or, in otherwords, an R-PDCCH unit. If interleaving is on, the R-PDCCH is mapped inunits of an REG or, in other words, an interleaving unit and arranged atpredetermined REG indexes. Therefore, if interleaving is on, one R-PDCCH(e.g. a DL grant) is distributed to a plurality of PRBs.

Referring to FIG. 25, DL grant interleaving/mapping and UL grantinterleaving/mapping may be performed independently. For example, a DLgrant may be mapped to the first slot of a PRB pair, while a UL grantmay be mapped to the second slot of the PRB pair. In the illustratedcase of FIG. 25, while DL grants are transmitted to RN 1, RN 2 and RN 3,UL grants may be transmitted only to RN 1 and RN 2. Then, the DL grantsare interleaved and mapped to a plurality of PRBs, and the UL grants arealso interleaved and mapped to a plurality of PRBs. As illustrated inFIG. 25, the R-PDCCH SS is preferably configured in PRB pairsirrespective of interleaving on/off. That is, it is preferred toconfigure the same RB sets for DL grants and UL grants (i.e. the same DLand UL SSs) irrespective of interleaving on/off.

In the presence of a DL grant in the first slot of a PRB pair, it may benecessary to indicate the use state of the second slot of the PRB pair(e.g. a UL grant, an (R-) PDSCH, empty, etc.). Thus, when a DL grant ispositioned in the first slot of a PRB pair, the presence or absence ofan R-PDSCH in the second slot of the PRB pair may be indicated by meansof an RA bit. In this case, an R-PDCCH for one RN resides preferably inone RBG. However, when the R-PDCCH is interleaved, it is distributed toa plurality of PRBs, thereby making it difficult to use an RA bitreliably. Accordingly, even though a UL grant is transmitted only to oneof RNs for which R-PDCCHs are jointly interleaved, the BS should notifythe RNs whether a UL grant is present in each of individual RBs to whichinterleaved UL grants are mapped.

For instance, even though the BS does not transmit a UL grant to RN 3,it should signal the state of the second slot to RN 3 if a UL grant SSis defined in a resource area allocated to an (R-)PDSCH for RN 3,because the BS transmits jointly interleaved UL grants of RN 1 and RN 2in the second slot. The use state of the second slot may be signaled byhigher-layer signaling (e.g. RRC signaling) or physical-layer signaling.Because the BS has knowledge of the presence or absence of aninterleaved R-PDCCH in an RB or RBG allocated to the (R-)PDSCH of RN 3,the BS rate-matches the (R-)PDSCH, taking into account an area having anR-PDCCH. One thing to note herein is that when RN 3 decodes the R-PDCCHarea, it should know the presence or absence of an R-PDCCH and thus theuse state of the second slot needs to be signaled to RN 3. It may befurther contemplated as another embodiment that areas of interleavedR-PDCCHs are always empty in the second slot, for system simplification.Specifically, RN 3 decodes a downlink signal on the assumption that thesecond slot of a DL SS is all a UL SS or is free of an (R-)PDSCH, andthe BS schedules based on the same assumption.

Multiplexing of Backhaul DL Data

If R-PDCCHs are interleaved for a plurality of RNs, this implies thatDL/UL grants of the RNs are interleaved. Thus, PRBs of RBGs carrying theDL grants need to be allocated carefully. In other words, collisionbetween RN data (e.g. (R-)PDSCHs) should be considered for PRBs otherthan R-PDCCH PRB pairs and collision between data and UL grants shouldbe considered for the second slots of the R-PDCCH PRBs.

First, a case where an RA bit for a specific RBG carrying a DL grant isset to 0 will be considered. In this case, it is preferred that the BSdoes not use any of the remaining PRB(s) of the RBG in order to avoidcollision between data transmitted to RNs. Although it is possible toallocate a remaining PRB pair of the RBG to another RN, each RN sharingthe interleaved DL grant cannot determine whether the PRB pair is usedfor another RN.

In the case where an RA bit for an RBG carrying a DL grant is set to 1,an RN expects the RBG to include data. The second slot of an R-PDCCH PRBpair may serve two usages depending on whether the second slot isdesignated as a UL grant SS or not. If the second slot of a PRB paircarrying a DL grant in its first slot is designated as a UL grant SS byhigher-layer signaling, data transmitted in the second slot of the PRBpair is highly vulnerable to interference caused by a UL grant foranother RN. That is, because an RN (RNs) is likely to receive a UL grantin the second slot of the R-PDCCH PRB pair, it is necessary not toallocate data to another RN in the second slot of the R-PDCCH PRB pairto avoid collision between the UL grant and the data. On the other hand,if the second slot of the R-PDCCH PRB pair is not designated as a ULgrant SS, data can be transmitted to the RN in the second slot of theR-PDCCH PRB pair.

Accordingly, resources may be allocated in the following manner. When anRA bit for an RBG carrying a DL grant is 0, a PRB (PRBs) other than aPRB carrying the DL grant is not used for data transmission in the RBG.On the contrary, if an RA bit for an RBG carrying a DL grant is 1, anon-R-PDCCH RBG pair in the RBG is used for RN data transmission,whereas the second slot of an R-PDCCH PRB pair is not used for RN datatransmission. In another method, if an RA bit for an RBG carrying a DLgrant is 1 and the second slot of an R-PDCCH PRB pair is designated as aUL grant SS in the RBG, the second slot of the R-PDCCH PRB pair is notused for data transmission. In any other case, the second slot of theR-PDCCH PRB pair is used for data transmission.

FIG. 26 illustrates an example of the afore-described resourceallocation. The example is based on the assumption that DL grants fortwo RNs, RN 1 and RN 2 are interleaved and allocated to R-PDCCH PRBs ofat least two RBGs. For the convenience' sake, RA bits for first andsecond RBGs are assumed to be 0 and 1, respectively. In Case 1, the RBGsinclude at least part of a UL grant SS, and in Case 2, the RBGs do notinclude a UL grant SS. The rule of allocating one RN per RBG andconfiguring an RBG into PRB pairs in an SS is also applicable even wheninterleaving is used.

Upon detection of a DL grant in the first slot, an RN can identify an RBor RBG allocated to it based on the relationship between the CCE indexof an R-PDCCH and a PRB. In this case, the RN can determine whether datais present in the second slot by interpreting an RB or RBG RA bitassociated with the PRB. For example, if CCEs are mapped to RBGs at 1:1or at A:B, the RN detects a CCE index and locates its PRB using the CCEindex. Then, the RN can determine the presence or absence of data in thesecond slot using an RA bit for the PRB. For instance, if a UL grant ispresent in the second slot, the RA bit may indicate no data. The otherPRB pairs except for the PRB in the RBG can be used for R-PDSCHtransmission.

FIG. 27 illustrates an example of R-PDCCH mapping in case ofinterleaving-off. When interleaving is off, an R-PDCCH for each RN ismapped on a CCE or slot basis without interleaving. If an R-PDCCHaggregation level increases, the number of PRBs for an R-PDCCH increaseswithin the same RBG. The aggregation levels of 2, 1 and 3 are set for RN1, RN 2 and RN 3, respectively in FIG. 27. If the aggregation level ofan RN exceeds the number of RBs set as an SS, it may be extended toanother SS RBG. For instance, given one RB per RBG as an SS, if theaggregation level is 4, the RN may achieve one R-PDCCH by performingblind decoding over 4 RBGs.

Within a backhaul RBG allocated for an R-PDCCH SS, the first RB may beused as the R-PDCCH SS, basically. Since different backhaul resourcesmay be allocated according to a channel state over time, a change in anSS is indicated preferably by RRC signaling. For example, if an RBGincludes 4 RBs, an R-PDCCH SS may be configured with up to 4 RBs perRBG. If an RBG includes 3 RBs, an R-PDCCH SS may be configured with upto 3 RBs per RBG. However, if only CCE aggregation levels 1 and 2, not 3are available, only 2 RBs per RBG may be designated as part of anR-PDCCH SS. FIG. 27 illustrates an example in which 4 RBs of an RBG areall designated as R-PDCCH transmission candidates on the assumption thateach RBG includes 4 RBs and a CCE aggregation level of 4 is supported.In the illustrated case of FIG. 27, RN 2 detects a DL grant from thefirst PRB of RBG 2, PRB #4 by blind decoding in an indicated R-PDCCH SS(RBG 2, RBG 3 and RBG 5).

In fact, every RBG used as backhaul resources may correspond to an SS.Accordingly, RBGs set as a backhaul resource area may be naturally setas an SS. Alternatively, only some RBGs of the backhaul resources may beset as an SS. Depending on real implementation, frequency resources(e.g. RBGs) may be allocated to an SS in various manners. For instance,if the indexes of resources allocated for backhaul communication areuniformly distributed such that the indexes of the frequency resourcesare odd-numbered, then even-numbered, and so on, an SS may be configuredonly with odd-numbered or even-numbered backhaul resources. It is alsopossible to configure an SS with every Nth frequency resource, startingfrom a frequency resource corresponding to a predetermined startingoffset.

SS Configuration Patterns and Signaling

FIG. 28 illustrates an example of configuring different SS RBs ordifferent SS RBGs over time. Since the frequency positions of backhaulresources may change over time, for the purpose of a frequency-selectivescheduling gain, different SS RBs or different SS RBGs may be configuredaccording to the changed backhaul resources. An SS may be alwaysconfigured in units of a PRB pair. In this case, the same mapping areamay be set for an interleaved or non-interleaved R-PDCCH (e.g. a DLgrant) in the first slot and an interleaved or non-interleaved R-PDCCH(e.g. a UL grant) in the second slot. That is, a DL grant SS and a ULgrant SS may be identical. Preferably, the DL grant SS and the UL grantSS may be identical only in non-interleaving mode. In addition, the ULgrant mapping area of the second slot may be equal to or smaller thanthe DL grant mapping area of the first slot. This means that the ULgrant mapping area may be a subset of the DL grant mapping area.

Referring to FIG. 28, a reference SS configuration is shown at theleftmost side. The reference SS configuration is an arbitrarily definedbasic SS configuration. Depending on implementations, a reference SSconfiguration may not be defined separately. In this example, an SS maychange over time, cell-specifically, RN group-specifically, orRN-specifically. As illustrated in FIG. 28, when an SS configuration setincludes SS configuration #1, SS configuration #2 and SS configuration#3, one of the SS configurations may be signaled to thereby change anexisting SS configuration. The SS configuration may be changedsemi-statically by higher-layer signaling (e.g. RRC signaling) ordynamically by physical-layer signaling.

If an SS is limited to one PRB (pair) per RBG, the PRB (pair) may be atany position in an RBG. However, considering RS-based demodulation, themiddle RB of an RBG is preferable for the SS to achieve betterperformance. For example, if an RBG includes 3 RBs, the second RB may beused for the SS. Similarly, if an RBG includes 4 RBs, the second orthird RB may be used for the SS. In this case, although the SS may befixed to the second or third RB, an RB used as the SS is preferablysignaled to thereby adapt the SS to an environment change. An RB usedfor an SS may be changed semi-statically by higher-layer signaling (e.g.RRC signaling) or dynamically by physical layer signaling.

For an SS configuration, the following information may be signaled.

1. Signaling of DM RS-based demodulation or CRS-based demodulation.

2. Signaling of interleaving mode or non-interleaving mode.

3. Signaling of the position of an SS RB in an RBG: e.g. for 4 RBs in anRBG, 1, 2, 3, or 4 among four positions is indicated.

4. Signaling of one of relay backhaul resource areas or boundaries: e.g.one of candidate boundaries is signaled.

While the above signals may be transmitted separately, they may betransmitted together in specific fields of the same RRC signal.

SS Configurations Based on RA Types

An R-PDCCH SS may be configured according to an RA type as follows. Asdescribed before with reference to FIGS. 7, 8 and 9, RA Types 0, 1 and 2are defined in legacy LTE. A description will first be given of RA Type2.

FIGS. 29 and 30 illustrate examples of configuring an R-PDCCH SSaccording to RA Type 2. In FIGS. 29 and 30, DVRBs are illustrated.Referring to FIGS. 29 and 30, the concept of an RBG subset may beintroduced to RA Type 2, for an SS configuration, like RA Type 1 oflegacy LTE. An R-PDCCH SS may be configured within the same RBG subsetfrom among resources allocated by RA Type 2. For example, if PRBs #0,#1, #2, #3, #16, #17, #18 and #19 form subset #0, an SS is configuredpreferably within the area of subset #0. Likewise, if PRBs #4, #5, #6,#7, #20, #21, #22 and #23 form subset #1, an SS is configured preferablywithin the area of subset #1.

FIG. 31 illustrates an example of configuring an R-PDCCH SS according toRA Type 0.

Referring to FIG. 31, only the concept of an RBG is used but the conceptof an RBG subset is not explicitly defined, in RA Type 0. Nonetheless,for an SS configuration, a BS/RN may regard RBGs #0, #3, #6 and #9 assubset #0, RBGs #1, #4, #7 and #10 as subset #1, and RBGs #2, #5 and #8as subset #2. As described before, it is preferred to configure anR-PDCCH SS within the same subset. Therefore, the R-PDCCH SS may bedefined in, for example, subset #0. If there are many R-PDCCHs, theR-PDCCH SS may be defined in subset #0 and subset #1. If more R-PDCCHsexist, the R-PDCCH SS may be defined in every subset. In most cases, onesubset, subset #k (k=0 to p) may be sufficient for the R-PDCCH SS.

FIG. 32 illustrates an example of configuring an R-PDCCH SS according toRA Type 1. Referring to FIG. 32, RA Type 1 is a typical RA type to whichthe concept of an RBG subset (shortly, a subset) is introduced. Asillustrated in FIG. 32, given a system band of 32 RBs, three subsets maybe configured. Preferably, the R-PDCCH SS is configured using RBGs ofthe same subset index, first of all. In FIG. 32, subset #0 includes RBGs#0, #3, #6 and #9. Hence, the R-PDCCH SS may be configured using RBGs#0, #3, #6 and #9. Whether all or part of the RBGs of subset #0 are usedis indicated by separate signaling or determined according to a presetpattern. It is also preferred to create a bitmap indicating a specificsubset and specific RBGs within the specific subset. For example, thebitmap may be created to indicate subset=0 and RBGs=0 and 6. Given 32RBs, a 6-bit signal suffices, including a subset indicator of 2 bits andan RBG bitmap indicator of 4 bits. This indication information may betransmitted semi-statically by RRC signaling. If a single subset is usedto configure the R-PDCCH SS, a specific subset (e.g. subset #0) ispreset as the single subset and thus only an RGB bitmap indicator may besignaled. If one or more subsets are used to configure the R-PDCCH SS,these subsets may be indicated by a bitmap. When the size of the bitmapis large, the subset indication information may be reduced bycompression, for example, by representing a starting subset and a subsetlength.

If the R-PDCCH SS is set within a single subset as described before,R-PDCCH SS RBs may be apart from one another by the square of P. P isthe number of RBs in an RBG. In the above example of 32 RBs, 11 RBGs maybe defined. Since each RBG includes 3 RBs, P=3. Accordingly, the R-PDCCHSS RBs may be disposed with a spacing of 9 RBs (=3²). If a plurality ofsubsets are used for the R-PDCCH SS, P² is the interval between SS RBsin each subset. The interval between subsets may be determined accordingto selected subsets and the number of the selected subsets.

In legacy LTE, the starting position of an SS is different for eachaggregation level. However, there is no need for differentiating thestarting position of an SS for an RN on a backhaul link according to anaggregation level. In this case, depending on a DCI payload size and asubblock interleaver size, the aggregation level of specific DCI may notbe determined and as a result, a PUCCH resource assignment generatedbased on CCE-to-ACK/NACK linkage may not be detected correctly. However,setting of a different starting position for an SS according to eachaggregation level causes difficulties in actual PRB mapping. While aPDCCH SS is mapped to contiguous PRBs in a control region, an R-PDCCH SSresides in non-contiguous PRBs and suffers from the constraint that a DLgrant and a UL grant exist in the same PRB pair. Therefore, blinddecoding for aggregation level N (e.g. 1) and blind decoding foraggregation level M (e.g. 2) start preferably at the same position.Consequently, there is no need for calculating a hash function each timethe starting position of blind decoding is to be determined according toan aggregation level.

The blind decoding starting positions of a DL grant and a UL grant maybe matched implicitly (or preset to be identical). That is, if anR-PDCCH SS for a DL grant has N CCEs in total, the total number of CCEsin an R-PDCCH SS for a UL grant may also be N. In this case, the indexof the starting position of the DL grant (e.g. a starting CCE index forDL grant blind decoding) may be reused as the index of the startingposition of the UL grant (e.g. a starting CCE index for UL grant blinddecoding), which obviates the need for calculating a hash function forthe UL grant.

If an SS is configured using one RB per RBG, the RB is preferablypositioned in the middle of an RBG. To simplify implementation, it isalso possible to set only one PRB located at one end of an RBG as an SS.However, if SS resources are allocated on an RBG basis, any RB of anallocated RBG is available as an SS.

Finally, if an RBG includes fewer RBs than P, an SS may be configuredonly with a predetermined number of RBs (N RBs, N<P) in an RBG. Forexample, the SS may be formed with N RBs counted from the first or thelast RB of each RBG.

Considering a shift in a subset in RA Type 1, it may occur that eventhough a subset includes Q RBGs, all of the Q RBGs is not indicated toan RN in relation to RA.

Therefore, the scheduler preferably maps an R-PDCCH, taking into accountthis case. Referring to FIG. 32, in case of subset #0 and shift #0, anRA bitmap actually indicates only RBGs #0, #3 and #6 out of RBGs #0, #3,#6 and #9. Hence, all of the RBGs need not be blind-detected on the partof an RN. Thus, three RBGs may be determined to be a maximum blinddecoding size in the above example. The maximum blind decoding size mayvary with a band. For instance, given 96 RBs, P=4 and a total of 25 RBGsare defined. Only part of the 25 RBGs are indicated in relation to RA.

FIGS. 33, 34 and 35 illustrate various examples of configuring anR-PDCCH SS in RBGs according to the foregoing methods. In FIGS. 33, 34and 35, an R-PDCCH SS is configured using RBGs within the same RBG set.Specifically, the R-PDCCH SS is configured with the middle RB pair ofeach RBG in an RBG subset in FIG. 33. In FIG. 34, two R-PDCCH SSs areconfigured in different RBG subsets. In addition, when the last RBGincludes fewer RBs than P, an SS may be configured only with apredetermined number of RBs (e.g. 2 RBs) in each RBG in FIG. 34. FIG. 35illustrates an example of configuring an SS using all RB pairs in eachof RBGs.

Common Search Space (CSS)

At least in a CRS-based R-PDCCH demodulation mode, a DL grant CSS and/ora UL grant CSS may be set. Preferably, a CSS may be set only for ULgrants. If both DL and UL grants are interleaved and a smaller number ofUL grants are paired with DL grants, the smaller number of interleavedUL grants are filled in PRB pairs, while the other areas of the PRBpairs are unused. This problem may be solved in the following methods.

One of the methods is that in case of partial (or full) interleaving,the second slots of PRB pairs (in an interleaving group) are not usedfor R-PDSCH transmission, in spite of only one UL grant interleaved inthe second slots of the PRB pairs. Unused REGs of the second slots maybe used by indicating distributed positions of REGs of the (interleaved)UL grant through signaling. Alternatively, the second slots of the PRBpairs may always be left empty irrespective of transmission of the(interleaved) UL grant.

Another method is that when a DL grant SS and a UL grant SS areindependently configured and a significant resource waste is expecteddue to a relatively small number of UL grants with respect to DL grantsirrespective of the positions of the DL grants, the UL grants may bedisposed in a CSS. According to this method, the second slots of PRBpairs carrying a plurality of DL grants can be used for another purpose(e.g. R-PDSCH transmission), thereby reducing resource waste. Meanwhile,some UL grants may be paired with DL grants and thus the paired UL andDL grants may be positioned in the same PRB pairs. Therefore, an RNfirst attempts to detect a DL grant in the first slot of an RB pair inorder to receive an R-PDCCH. Upon detection of the DL grant in the firstslot, the RN attempts to detect a UL grant in the second slot of the RBpair. If the RN fails in detecting a UL grant in the RB pair, the RNattempts to detect a UL grant in a UL grant CSS configured in the secondslot.

A third method is to differentiate a DL grant interleaving size from aUL grant interleaving size. For instance, DL grants may be partiallyinterleaved in units of 4 RBs, whereas UL grants may be partiallyinterleaved in units of 2 RBs. To facilitate DL and UL grantinterleaving of different sizes, a DL grant resource area and a UL grantresource area should be managed independently. As stated before, when aUL grant CSS is used, interleaving can be performed for DL and UL grantsaccording to different interleaver sizes.

Referring to FIG. 36, reference characters A and B denote a DL grant SSand a UL grant SS, respectively. The DL grant SS may be a dedicated SS(DSS) and the UL grant SS may be a CSS. For example, if DM RSs are used,a DSS may be configured. If CRSs are used, a CSS may be configured. Itmay be indicated by signaling whether an SS is a DSS or a CSS.

CCE Aggregation Levels Based on RBG Size

An RBG size depends on a system BandWidth (BW). In LTE, four RBG sizes,1, 2, 3 and 4 RBs are defined according to system BWs. If a system BWincludes 64 to 110 RBs to ensure backward compatibility with legacy LTE,each RBG includes 4 RBs. Accordingly, the CCE aggregation levels ofR-PDCCHs may be limited to one or more sets of {1, 2, 3, 4}, {1, 2, 3,},{1, 2, 4}, or {1, 2} (e.g. 1 CCE=1 RB). An example of R-PDCCHtransmission in a system BW of 64 to 100 RBs is illustrated in FIG. 37.If the BW includes 27 to 63 RBs, the RBG size is 3 RBs and thus the CCEaggregation levels of R-PDCCHs may be limited to one or more sets of {1,2, 3}, {1, 2}, and {1, 3}. If the BW includes 11 to 26 RBs, the RBG sizeis 2 RBs and thus the CCE aggregation levels of R-PDCCHs may be limitedto one or more sets of {1, 2}, {1}, and {2}. It is possible to set 1, 2,3 and 4 available as the CCE aggregation levels of R-PDCCHs and then tolimit the highest CCE aggregation level to one of the values, to coverall cases. For example, different aggregation levels may be supportedaccording to BWs.

Table 4 illustrates supportable aggregation levels for different BWs.

TABLE 4 System BW [RB] Supportable aggregation level 64 to 110 1, 2, 3,4 27 to 63 1, 2, 3 11 to 26 1, 2 <=10 1 or not supported

Interleaving and Mapping for R-PDCCH

FIG. 38 illustrates an exemplary mapping operation for R-PDCCHtransmission. This example is characterized in that an R-PDCCH isinterleaved and mapped to a PDSCH area according to a VRB-to-PRB mappingrule in order to transmit the R-PDCCH in the PDSCH area, instead of anLTE PDCCH area. For the R-PDCCH transmission, various interleavingschemes and various mapping schemes can be used. It is also possible tosubject CCEs to interleaving (partial interleaving) on a group basis andthen map the interleaved CCEs based on the operation of FIG. 38. On thepart of an RN, an operation for detecting an R-PDCCH in one or morepartial-interleaved areas may be included.

FIG. 38 is based on the assumption that an area in which an R-PDCCH(R-PDCCHs) corresponding to 8 CCEs can be transmitted is semi-staticallysignaled and the R-PDCCH is actually transmitted in resourcescorresponding to 6 CCEs (all or each of 6 CCEs may be used by one RN).The size of a CCE may be different according to a normal CP or anextended CP or according to a CRS mode or a DM RS mode. Herein, it isassumed that 8 REGs of a PRB in the first slot are available and definedas one CCE in case of a normal CP/a DM-RS mode. In the illustrated caseof FIG. 38, a bandwidth includes 50 RBs and one PRB per RBG (1 RBG=3RBs) is used for R-PDCCH transmission. The RBG size may be determined asdefined in legacy LTE.

Interleaving & Permutation

In Method 1, 8 CCEs including nulls are interleaved (including columnpermutation in a column permutation pattern). Bit reversal is an exampleof the column permutation pattern. For reference, an RN-specific SS(within a logical CCE index domain) is basically assumed. Method 2 willbe described later. Method 3 is different from Method 1 in that one ormore interleaving units are used. For instance, 8 CCEs are divided intoa plurality of parts (e.g. two parts each having 4 CCEs) and interleavedin Method 3. Meanwhile, if RB-level permutation is performed duringVRB-to-PRB mapping (e.g. using bit reversal), REG-level columnpermutation or bit reversal may be omitted during interleaving, whichdoes not much affect performance. For reference, an SS in a logical CCEdomain is assumed to be a CSS accessible to all RNs in Method 3. The useof an RN-specific SS may slightly decrease operation efficiency orresource efficiency, but does not limit the implementation of thepresent invention.

After interleaving and permutation, an R-PDCCH is mapped to PRBsaccording to various rules. To describe the mapping, the concept of VRBmay be used. In the example of FIG. 38, 8 REGs being 1, 33, 17, N, 9,41, 25, N (N is a null REG) among values (outputs) read column by columnafter interleaving and permutation form one VRB. While a VRB and a CCEare equal in size in FIG. 38, the same performance may be achieved eventhough the VRB size is larger than the CCE size. Even in case of anormal CP, the following various numbers of REGs are available.Therefore, the CCE size and the VRB size may be changed based on thenumber of available REGs per RB according to a transmission mode, asfollows.

1^(st) slot:

-   -   8 REGs in the 1^(st) slot (e.g. DM RS used)    -   11 REGs in the 1^(st) slot (e.g. CRS used)

2^(nd) slot:

-   -   15 REGs in the 2^(nd) slot (e.g., DM RS used and 4TX CRS)    -   16 REGs in the 2^(nd) slot (e.g. DM RS used and 2TX CRS)    -   18 REGs in the 2^(nd) slot (e.g. CRS used and 4TX CRS)    -   19 REGs in the 2^(nd) slot (e.g., CRS used and 2TX CRS)

For example, when a DL grant is transmitted in the first slot, the DLgrant is interleaved by defining one CCE as 8 REGs. A VRB size may bedefined as 8 REGs in case of DM RSs and as 11 REGs in case of CRSs.According to this method, a detection operation may be facilitated byfixing the CCE size. In addition, the VRB size is set to an optimumvalue (e.g. the number of available REGs) to efficiently use the numberof available REGs which varies according to an RS mode. Therefore,resource waste can be minimized.

It is also preferred to define VRB sizes as 15, 16, 17 and 19 REGs inactual VRB-to-PRB mapping, with a CCE size given as 8 REGs, in thesecond slot. The size of one VRB is given as an example according to achange in RSs and TX antennas. The VRB size may be changed despite thesame logic and rule.

VRB-to-PRB Mapping

The simplest mapping rule is to sequentially map VRB indexes to R-PDCCHPRB indexes (renumbered indexes only for R-PDCCH RBs or indexes labeledin an R-PDCCH area in FIG. 38) at 1:1. Despite its simplicity, thismapping rule causes localization of jointly interleaved CCEs in a partof an R-PDCCH PRB (R-PDCCH PRBs). The localization may not matter if thepart includes 4 or more PRBs, while it may cause a problem with adiversity gain if the part includes 3 or fewer PRBs.

In another method, permutation may be performed (e.g. by bit reversal)at an RB level. This method is simple and maps VRBs uniformly to PRBs.For example, if a total of four R-PDCCH PRBs exist, VRB #0 (00), VRB #1(01), VRB #2 (10), and VRB #3 (11) may be mapped to R-PDCCH PRBs #0(00), #2 (10), #1 (01), and #3 (11), respectively. If the number ofR-PDCCH PRBs is not 2^(N), VRBs may be mapped to the R-PDCCH PRBs bysuch a method as pruning, while the bit reversal rule is maintained.When bit reversal is applied, it is preferable not to use columnpermutation (e.g. REG-level bit reversal) during interleaving. However,only if implementation complexity permits, both REG-level bit reversaland RB-level bit reversal may be applied.

In a further method, a rule that enables even distribution may be used.For example, a VRB index i may be mapped to a PRB index f(i) by Equation4. In Equation 4, N represents the size of a physical R-PDCCH area (e.g.in PRBs) and K represents the size of an actual R-PDCCH to betransmitted (e.g. in PRBs). Even when a VRB and a PRB differ in thenumber of available REs, K is calculated in terms of PRBs. Herein, a, band c are constants.

$\begin{matrix}{{f(i)} = {{c*\lfloor \frac{{i*N} + a}{K} \rfloor} + b}} & \lbrack {{Equation}\mspace{14mu} 4} \rbrack\end{matrix}$

Table 5 and Table 6 illustrate examples of VRB-to-PRB mapping accordingto [Equation 4]. Table 5 illustrates VRB-to-PRB mapping when K=7, N=16,a=b=0, and c=1. That is, Table 5 illustrates mapping of VRB indexes 0 to7 (8 RBs, K=7) to R-PDCCH PRB indexes 0 to 16 (17 RBs, N=16) and Table 6illustrates VRB-to-PRB mapping when K=7 and N=24.

TABLE 5 VRB index 0 1 2 3 4 5 6 7 PRB index 0 2 4 6 9 11 13 16 (R-PDCCH)

TABLE 6 VRB index 0 1 2 3 4 5 6 7 PRB index 0 3 6 10 13 17 20 24(R-PDCCH)

The mapping patterns may be modified through shifting or by adjusting amapping interval using the additional parameters, a, b and c in[Equation 4].

While REG-to-PRB mapping is not described in detail in FIG. 38, theREG-to-PRB mapping may be carried out in various manners. For example,REGs may be mapped to a PRB in a frequency-first mapping rule, asillustrated in FIG. 38. However, the mapping pattern may vary accordingto an actual REG configuration and actual indexing.

Frequency-first mapping may be performed across total R-PDCCH PRBs. Thenan interleaved result as illustrated in FIG. 39 may be achieved. In FIG.39, CCE 0 and CCE 4 exist in R-PDCCH PRBs #0 and #4 only. Each CCE ispresent only in an R-PDCCH RBG with an index corresponding to the CCE.Therefore, a diversity gain problem may occur. If the VRB size isdifferent from the PRB size, mapping may be performed in a differentmanner.

Meanwhile, time-first mapping may be performed within each R-PDCCH PRB.FIG. 40 illustrates an example of time-first mapping.

Interleaving and mapping method 2 is almost identical to the method ofFIG. 38 from the perspective of transmission, except that an RN shouldadditionally perform blind decoding according to interleaving depths inorder to detect an interleaving depth because the RN does not know thenumber of RBs as an interleaving unit. Despite this shortcoming,interleaving and mapping method 2 can dynamically optimize resources bysetting an interleaving depth equal to the size of an R-PDCCH to betransmitted (e.g. in RBs), when possible. If the interleaving depth is 1RB, the size of an actual R-PDCCH to be transmitted may equal to theactual interleaving depth. Notably, it is preferred to presetinterleaving depths with a predetermined granularity, such as 8 RBs, 12RBs, etc. in order to reduce the number of blind decodings forinterleaving depths. This information may be set by RRC signaling. If anR-PDCCH area includes 16 RBs and only {8 RBs, 16 RBs} are available asinterleaving depths, one of various sets such as {4 RBs, 8 RBs, 16 RBs},{4 RBs, 8 RBs, RBs, 16 RBs}, {4 RBs, 16 RBs} may be preset by signaling.

This signaling scheme may be used when an RN determines a monitoring setin Method 3. That is, one of set 1, set 2 and even full sets may besignaled to an RN, as an appropriate monitoring set. This scheme can beused to signal an RN monitoring set in almost all proposed methods.

Methods 1, 2 and 3 are based on the assumption of a fixed interleavercolumn size. However, the fixed interleaver column size is purelyexemplary and the column size may be variable. For instance,interleaving may be performed in an interleaver with a column size of16.

RN-Specific CCE Indexing

The foregoing methods have been described so far on the premise that CCEindexes are cell-specific. On the other hand, CCE indexes may be definedRN-specifically. In FIG. 38, CCE 0 to CCE 3 and CCE 4 to CCE 7 areRN-specifically interleaved separately and it is assumed that eachinterleaving group includes CCE 0 to CCE 3. As a result, CCE 0 of group1 is different from CCE 1 of group 2. Only when information required todistinguish CCE 0 of group 1 from CCE 0 of group 2 is signaled to an RN,the RN may calculate BS-specific (or cell-specific) CCE indexes. SinceBS-specific CCE indexes are used for determining RN PUCCH resources fortransmission of a UL ACK/NACK, they should be defined cell-specificallyto avoid overlapped resource allocation or resource waste. Instead ofadditionally transmitting a group index for RN PUCCH resources, the RNPUCCH resources may be allocated by group and the starting RB ofallocated RN PUCCH resources may be signaled. For reference, RN PUCCHresources are assumed to be linked to an R-PDCCH CCE index (e.g. aminimum CCE index for an R-PDCCH).

Interleaving and Mapping Method 4

FIG. 41 illustrates an R-PDCCH mapping operation in Method 4. Accordingto Method 4, permutation is uniformly performed (e.g. by bit reversal)during VRB-to-PRB mapping, without column permutation duringinterleaving. In Method 4, an interleaver column size is defined as thenumber of REGs in a CCE and an interleaver row size is changed accordingto the number of CCEs to be interleaved. REGs extracted from 8 differentCCEs form one VRB (herein, 1 VRB=8 REGs). If the number of R-PDCCH RBsis not 2^(N) (N=1, 2, 3, . . . ), mapping may be performed by bitreversal pruning. The interleaver column size characteristic of thismethod is also applicable to Methods 1, 2 and 3.

Interleaving and Mapping Method 5

FIG. 42 illustrates an exemplary R-PDCCH mapping operation in Method 5.According to Method 5, column permutation is performed duringinterleaving and VRB-to-PRB mapping is performed simply withoutpermutation (e.g. bit reversal). [Equation 4] is also applicable toMethod 5. The interleaver column size is defined as the number of REGsin a CCE and the interleaver row size is changed according to the numberof CCEs to be interleaved.

An RN may demodulate an R-PDCCH/R-PDSCH in various manners according toa mode supported for a relay backhaul link (a Un link), as illustratedin Table 7.

TABLE 7 R-PDCCH/R-PDSCH demodulation RS 1st slot 2nd slot Case demod.deomod Supporting modes Subframe 1 CRS CRS Mode 1-1 and 2 Normal (NCP,ECP) DL grant R-PDSCH 2 CRS CRS Mode 1-1 and 2 Normal (NCP, ECP) DLgrant UL grant 3 CRS DM RS CRS Mode 2 Normal (NCP, ECP) DL grant R-PDSCH4 DM DM RS DM RS mode 2 Normal (NCP, ECP) RS DL grant R-PDSCH 5 DM DM RSDM RS mode 2 Normal (NCP, ECP) RS DL grant UL grant 6 DM CRS DM RS mode2 Normal (NCP, ECP) RS DL grant R-PDSCH 7 DM DM RS DM RS mode 2 MBSFN(ECP) RS DL grant R-PDSCH 8 DM DM RS DM RS mode 2 MBSFN (ECP) RS DLgrant UL grant

Referring to Table 7, an R-PDCCH exists in the first slot, a CRS is usedas an R-PDCCH demodulation RS, an R-PDSCH exists in the second slot, anda CRS is used as an R-PDSCH demodulation RS in Case 1. It is preferredin Case 1 that an RN performs CRS-based demodulation and operates in anR-PDCCH interleaving mode (CRS mode 1-1) and an R-PDCCH non-interleavingmode (CRS mode 2). In addition, a normal subframe is used and both anormal CP and an extended CP are supported in Case 1.

Case 4 uses DM RSs to demodulate a DL grant (an R-PDCCH) in the firstslot and an R-PDSCH in the second slot. Case 4 is suitable for anon-interleaving mode ‘DM RS mode 2] (Mode 2D or replaceable with someother term).

In Cases of Table 7 performing interleaving, the BS needs to determinethe number of R-CCEs, PRBs or RNs that are subject to jointinterleaving. The number of R-CCEs, PRBs or RNs determined forinterleaving may be referred to as an interleaver size or interleavingdepth. Despite interleaving on an RN basis, the BS may interleave moreCCEs than the RNs according to the CCE aggregation levels (e.g. 1, 2 and4) of the RNs. The interleaved CCEs may be mapped to PRBs. Theinterleaver size may be in, but not limited to, RBs or CCEs.

FIG. 43 illustrates an exemplary mapping operation for R-PDCCHtransmission.

The BS may interleave an R-PDCCH for an RN at an R-CCE or REG level.This embodiment is characterized in that an R-PDCCH is interleaved andmapped to a PDSCH area according to a VRB-to-PRB mapping rule in orderto transmit the R-PDCCH in the PDSCH area, instead of an LTE PDCCH area.For the R-PDCCH transmission, various interleaving schemes and variousmapping schemes are available. It is also possible to subject CCEs tointerleaving (partial interleaving) on a group basis and then map theinterleaved CCEs based on the operation of FIG. 43. On the part of anRN, an operation for detecting an R-PDCCH in one or morepartial-interleaved areas may be included.

As illustrated in FIG. 43, an interleaving depth is assumed to be 8CCEs. FIG. 43 is based on the assumption that an area in which anR-PDCCH (R-PDCCHs) corresponding to 8 CCEs (for example, if 1 CCC=8 REG)can be transmitted is semi-statically signaled and the R-PDCCH isactually transmitted in resources corresponding to 6 CCEs (6 CCEs may beused, all by one RN or one by each RN). The size of a CCE may bedifferent depending on a normal or extended CP or depending on a CRSmode or a DM-RS mode. Herein, it is assumed that 8 REGs of a PRB in thefirst slot are available and defined as one CCE in case of a normalCP/DM-RS mode. In the illustrated case of FIG. 38, a BW includes 50 RBsand one PRB per RBG (1 RBG=3 RBs) is used for R-PDCCH transmission. TheRBG size may be determined as defined in legacy LTE. 1 CCE includes howmany number of REG (for example, 1 CCE=8REG, 1 CCE=9 REG) may varyaccording to cyclic prefix and configuration of RS in RB

Interleaving & Permutation

In Method 1, 8 CCEs including nulls are interleaved (including columnpermutation in a column permutation pattern). Bit reversal is an exampleof the column permutation pattern. For reference, an RN-specific SS(within a logical CCE index domain) is basically assumed. Method 2 willbe described later. Method 3 is different from Method 1 in that one ormore interleaving units are used. For instance, 8 CCEs are divided intoa plurality of parts (e.g. two parts each having 4 CCEs) and interleavedin Method 3. Meanwhile, if RB-level permutation is performed duringVRB-to-PRB mapping (e.g. using bit reversal), REG-level columnpermutation or bit reversal may be omitted during interleaving, whichdoes not much affect performance. For reference, an SS in a logical CCEdomain is assumed to be a CSS accessible to all RNs in Method 3. The useof an RN-specific SS may slightly decrease operation efficiency orresource efficiency, but does not limit the implementation of thepresent invention.

After interleaving and permutation, an R-PDCCH is mapped to PRBsaccording to various rules. To describe the mapping, the concept of VRBmay be used. In the example of FIG. 43, 8 REGs being 1, 33, 17, N, 9,41, 25, N (N is a null REG) among values (outputs) read column by columnafter interleaving and permutation form one VRB. While a VRB and a CCEare equal in size in FIG. 38, the same performance may be achieved eventhough the VRB size is larger than the CCE size. Even in case of anormal CP, the following various numbers of REGs are available.Therefore, the CCE size and the VRB size may be changed based on thenumber of available REGs per RB according to a transmission mode, asfollows.

1^(st) slot:

-   -   8 REGs in the 1^(st) slot (e.g. DM RS used)    -   11 REGs in the 1^(st) slot (e.g. CRS used)

2^(nd) slot:

-   -   15 REGs in the 2^(nd) slot (e.g., DM RS used and 4TX CRS)    -   16 REGs in the 2^(nd) slot (e.g. DM RS used and 2TX CRS)    -   18 REGs in the 2^(nd) slot (e.g. CRS used and 4TX CRS)    -   19 REGs in the 2^(nd) slot (e.g., CRS used and 2TX CRS)

For example, when a DL grant is transmitted in the first slot, the DLgrant is interleaved by defining one CCE as 8 REGs. A VRB size may bedefined as 8 REGs in case of DM RSs and as 11 REGs in case of CRSs.According to this method, a detection operation may be facilitated byfixing the CCE size. In addition, the VRB size is set to an optimumvalue (e.g. the number of available REGs) to efficiently use the numberof available REGs which varies according to an RS mode. Therefore,resource waste can be minimized.

It is also preferred to define VRB sizes as 15, 16, and 19 REGs inactual VRB-to-PRB mapping, with a CCE size given as 8 REGs, in thesecond slot. The size of one VRB is given as an example according to achange in RSs and TX antennas. The VRB size may be changed despite thesame logic and rule.

VRB-to-PRB Mapping

The simplest mapping rule is to sequentially map VRB indexes to R-PDCCHPRB indexes (renumbered indexes only for R-PDCCH RBs or indexes labeledin an R-PDCCH area in FIG. 38) at 1:1. Despite its simplicity, thismapping rule causes localization of jointly interleaved CCEs in a partof an R-PDCCH PRB (R-PDCCH PRBs). The localization may not matter if thepart includes 4 or more PRBs, while it may cause a problem with adiversity gain if the part includes 3 or fewer PRBs.

In another method, permutation may be performed (e.g. by bit reversal)at an RB level. This method is simple and maps VRBs uniformly to PRBs.For example, if a total of four R-PDCCH PRBs exist, VRB #0 (00), VRB #1(01), VRB #2 (10), and VRB #3 (11) may be mapped to R-PDCCH PRBs #0(00), #2 (10), #1 (01), and #3 (11), respectively. If the number ofR-PDCCH PRBs is not 2^(N), VRBs may be mapped to the R-PDCCH PRBs bysuch a method as pruning, while the bit reversal rule is maintained.When bit reversal is applied, it is preferable not to use columnpermutation (e.g. REG-level bit reversal) during interleaving. However,only if implementation complexity permits, both REG-level bit reversaland RB-level bit reversal may be applied.

In a further method, a rule that enables even distribution may be used.For example, a VRB index i may be mapped to a PRB index f(i) by Equation4.

While REG-to-PRB mapping is not described in detail in FIG. 43, theREG-to-PRB mapping may be carried out in various manners. For example,REGs may be mapped to a PRB in a frequency-first mapping rule, asillustrated in FIG. 43. However, the mapping pattern may vary accordingto an actual REG configuration and actual indexing.

As described above, after VRBs are configured, they may be mapped toPRBs. Because the BS indicates the positions of PRBs to an RN or an RNgroup by RRC signaling, the RN or RN group may decode an R-PDCCH at theindicated PRB positions. It is assumed that the BS performs a pluralityof interleaving operations. That is, the BS may divide RNs into aplurality of RN groups and perform interleaving by RN group. An RNwithin a specific group has only to find out a mapping scheme applied tothe specific group or the logical indexes of mapped positions. Thisinformation may be indicated by RN-specific or RN group-specific RRCsignaling. On the part of the RN, there is only one SS. The RN has onlyto find out the SS without the need for determining whether the SS isRN-specific or cell-specific. The BS does not need to indicate to the RNwhether the SS is RN-specific or cell-specific, either.

Table 8 lists exemplary interleaving depths that are available ordefined for given system BWs.

TABLE 8

Referring to Table 8, No. of different interleavers (A) specifies thenumber of interleavers having different depths (in terms of size), withequal-sized interleavers for a given system BW excluded. For instance,there are a total of 10 interleavers for a system BW of 20 MHz. In theproposed method of Table 8, if an interleaver size is equal to or largerthan 20 RBs, a plurality of interleavers having a smaller size than 20RBs are used for interleaving. No. of special/extra interleaver (B)means that while an interleaver is configured basically with aninterleaver size of 4 RBs or a multiple of 4 RBs, 2 RBs are sufficientfor 1.4 MHz and thus a 2-RB interleaver is supported. The value of No.of special/extra interleaver (B) may be used for other system bandwidthsto reduce the granularity of an interleaver size and minimize resourcewaste. No. of basic unit interleavers (C) indicates the number of basicunit interleavers. When one interleaving is performed in a given systemBW according to one interleaver size, the interleaving depth is equal tothe interleaver size. This interleaver size may be said to be a basicunit of interleaver. No. of concatenated interleavers (D) specifies thesum of the sizes of concatenated basic unit interleavers. When aninterleaving depth is increased, it is better to deal with the increasedinterleaving depth by grouping RNs into a plurality of groups and usinga plurality of basic unit interleavers for the groups, rather than touse an interleaver of the increased interleaver size. Total (E)indicates the total number of interleaving depths including singleinterleaving and concatenated interleaving.

As illustrated in Table 8, a total of 11 interleaving depths/sizes maybe used, which are 2, 4, 8, 12, 16, 20, 24, 28, 32, 48 and 80. In thesystem BW of 1.4 MHz corresponding to 6 RBs, an interleaving unit of 2or 4 RBs may be preferable. When interleaving is to be performed in asituation where only one or two RNs exist, 2, 3, 4, 5 and 6 RBs areavailable as an interleaving unit. However, if the interleaving unit is6 RBs, all RBs should be used for R-PDCCH transmission, which is notpreferable. Thus 2 or 4 RBs are appropriate as the interleaving unit. If1-CCE R-PDCCHs are configured for RNs and the size of an R-CCE equalsthe size of a VRB, interleaving with an interleaving unit of 2 or 4 RBsmay be referred to as 2-RB interleaving or 4-RB interleaving, or 2-RNinterleaving or 4-RN interleaving.

If Type 2 DVRB RA is supported, 4-RB interleaving may lead to efficientresource allocation between an RN and a macro UE or between RNs (ofdifferent RA types). RA Types 0, 1 and 2 are designed such that they canbe multiplexed in the same subframe, and if the size of DVRBs is amultiple of 4 RBs, resources are allocated in PRB pairs despite slothopping. Therefore, a PRB pair in the same frequency area may beallocated to an RN. In addition, considering only CCE aggregation levelsof 1, 2 and 4, the size of DVRBs is preferably a multiple of 4 RBs,instead of a multiple of 3 or 5 RBs. In a special case, a multiple of 2RBs may be supported.

From the viewpoint of R-PDCCH PRB set signaling, signaling overhead canbe reduced significantly by allocating one bit per RBG rather thansignaling PRBs of the total band in a bitmap. An SS may be allocated inunits of an RBG by setting an RBG size to 3 or 4 RBs. For instance,while a 100-bit bitmap is required for 100 RBs, a 25-bit bitmap sufficesin case of RBG-based signaling, if 1 RBG=4 RBs. However, as the BWdecreases, the RBG size also decreases. Accordingly, the number ofR-PDCCH PRB candidates decreases in proportion to the RBG size. In thiscase, there is no problem with RBG=3 if 27<RB<63 and with RBG=4 if64<RB<110. On the other hand, some problem may occur if 11<RB<26 (RBG=2)or RB≦10 (RBG=1). Then, it is preferred to form a bitmap having one bitper 3 RBs if 11<RB<26 and a bitmap having one bit per 2 RBs if RB≦10.

For implementation simplicity, a bitmap is formed preferably on an RBGbasis. Obviously, the number of R-PDCCH PRB candidates depends on thenumber of actually used RBs (a system BW). For example, for 64 RBs, 16REGs are defined, 16 PRBs are R-PDCCH PRB candidates, and thus a 16-bitbitmap is needed. For 110 RBs, 28 RBGs (27 RBGs=108 RBs and theremaining 2 RBs form 1 RBG) are formed and thus a 28-bit bitmap isrequired. For example, the bitmap with a fixed size of 28 bits may betransmitted by RRC signaling. In this manner, bitmaps of different sizesmay be used even for the same RBG size (e.g. 1 RBG=4 RBs). The requiredsize of a bitmap is given byCeiling {number of RBs(number of system RBs or available RBs or totalRBs)/RBG size}  [Equation 5]

In [Equation 5], Ceiling is a function of rounding up a value within { }to the nearest integer. For example, if 110/4=27.5, 27.5 is rounded upto 28. To simplify the design of RRC bitmap signaling, the number of RRCsignaling bits is kept to K (e.g. 28) and if a system BW changes, somebitmap bits are reserved. Or a bitmap is designed based on a maximumsystem BW for the same RBG size and commonly applied to all BWs usingthe same RBG size. Table 9 lists RBG sizes and bitmap sizes according tosystem BWs.

TABLE 9 System Bitmap Bitmap Bitmap Bitmap Bitmap Bitmap Bitmap RBGbandwidth size size size size size size size size [RB] [bit] [bit] [bit][bit] [bit] [bit] [bit] 1 RB ≦ 10 10 28 10[16] 10 13 32 16 2 11 ≦ RB ≦26 13 28 28[32] 13 13 32 16 3 27 ≦ RB ≦ 63 21 28 28[32] 28 28 32 32 4 64≦ RB ≦ 110 28 28 28[32] 28 28 32 32

Blind Decoding

Given a system BW of 20 MHz, a BS may perform interleaving withinterleaver sizes of 4, 8, 12, 16, 20, 24, 28, 32, 48 and 80.Considering that control information hardly occupies 80 RBs out of 100RBs in real implementation, the interleaver size of 80 may be neglected.

It is possible to use only unit interleavers except for interleavingdepths achieved through concatenated interleavers illustrated in Table8. Concatenated interleavers are optional.

FIG. 44 illustrates exemplary positions and frequency areas of blinddecoding, for interleaving depths of 4, 8, 12 and 16.

Referring to FIG. 44, only the interleaving depths of 4, 8, 12 and 16may be used for the given system BW of 20 MHz. When needed, aninterleaving depth of 2 may be added. In this case, when only CCEaggregation levels of 1, and 4 are supported, an RN may perform fourblind decodings (at 4 positions) for the CCE aggregation level of 4, 8blind decodings (at 8 positions) for the CCE aggregation level of 2, and16 blind decodings (at 16 positions) for the CCE aggregation level of 1.Therefore, the total number of blind decodings is 28 (=4+8+16). If twotypes of DCI formats are supported, the number of blind decodings thatthe RN should perform is doubled to 56. This value is approximate to thenumber of blind decodings performed at a UE conforming the 3GPPRelease-10 communication standard and thus may be considered reasonable.

FIG. 45 illustrates another example of positions and frequency areas ofblind decoding, for interleaving depths of 4, 8, 12 and 16.

The design of FIG. 45 may be preferable in terms of the blind decodingcomplexity of the 3GPP Release-8 communication standard. An RN mayperform 3 blind decodings (at 3 positions) for the CCE aggregation levelof 4, 6 blind decodings (at 6 positions) for the CCE aggregation levelof 2, and 12 blind decodings (at 12 positions) for the CCE aggregationlevel of 1. If another DCI format is supported, the total number ofblind decodings is 42, approximate to 44 blind decodings performed at aRelease-8 UE.

FIG. 46 illustrates a further example of positions and frequency areasof blind decoding, for interleaving depths of 4, 8, 12 and 16.

16 blind decodings may be maintained for the CCE aggregation level of 1as in the illustrated case of FIG. 44, while the number of blinddecodings may be reduced for the CCE aggregation level of 2 or 4.Referring to FIG. 46, for example, an RN may perform 6 blind decodings(at 6 positions) for the CCE aggregation level of 2 and 3 blinddecodings (at 3 positions) for the CCE aggregation level of 4.Therefore, the total number of blind decodings is 25 (=16+6+3).

In addition, as different aggregation starting positions and differentblind decoding position are set for different aggregation levels,overlapping between the SSs of RNs or error decoding at an unintendedCCE aggregation level in the same RN can be reduced. In FIG. 46,position overlapping is avoided by setting an offset at least betweenthe CCE aggregation levels of 2 and 4.

The configuration of FIG. 46 is characterized in that SSs may reside atdifferent positions (that is, blind decoding may start at differentpoints) for different aggregation levels. In addition, after an SS isconfigured for an RN or a UE, the SS may be changed in a specific orarbitrary pattern. In other words, a plurality of SS sets (e.g. VRBsets) are set and an SS may be modified within the SS sets. Especially,this modification or modified pattern is made based on an RN ID or a UEID. Thus the RN or the UE may determine the modification or modifiedpattern using the RN ID or the UE ID.

The above-described methods do not consider uplink grant blind decoding.As a DL grant is logically or physically linked to a UL grant,successful blind decoding of the DL grant enables decoding of the ULgrant implicitly tied to the DL grant, thereby reducing the number ofblind decodings. That's why all blind decoding complexity has beenconsidered regarding the DL grant blind decoding. Otherwise, the blinddecoding complexity may be doubled.

Table 10 to Table 22 illustrate modifications of the interleaver setproposed in Table 8. They are mostly designed such that [the number ofinterleaving depths×the number of system BWs] is approximate to 18.

TABLE 10

<Proposed Interleaver Set #2>

Referring to Table 10, 2, 4, 8, 12 and 16 are used as interleavingdepths/sizes for each given system BW.

TABLE 11

<Proposed Interleaver Set #3>

Referring to Table 11, 2, 4, 8, and 12 are used as interleavingdepths/sizes for each given system BW.

TABLE 12

<Proposed Interleaver Set #4>

Like Table 11, 2, 4, 8, and 12 are used as interleaving depths/sizes foreach given system BW in Table 12.

TABLE 13

<Proposed Interleaver Set #5 >

2, 4, 8, and 12 are also used as interleaving depths/sizes for eachgiven system BW in Table 13.

TABLE 14

<Proposed Interleaver Set #6>

2, 4, 8, and 12 are also used as interleaving depths/sizes for eachgiven system BW in Table 14.

TABLE 15

<Proposed Interleaver Set #7>

2, 4, 8, 12 and 16 are used as interleaving depths/sizes for each givensystem BW in Table 15.

TABLE 16

<Proposed Interleaver Set #8>

2, 4, 8, 12 and 16 are used as interleaving depths/sizes for each givensystem BW in Table 16.

TABLE 17

<Proposed Interleaver Set #9>

TABLE 18

<Proposed Interleaver Set #10>

TABLE 19

<Proposed Interleaver Set #11>

TABLE 20

<Proposed Interleaver Set #12>

TABLE 21

<Proposed Interleaver Set #13>

TABLE 22

<Proposed Interleaver Set #14>

The above interleaver sets are applicable to UL grant blind decoding aswell as DL grant blind decoding. If an uplink R-PDCCH SS is determinedrelying on DL grant blind decoding without UL grant blind decoding, theproposed interleaver sets are DL grant-dedicated. However, the proposedinterleaver sets may also be used as UL grant-dedicated.

The above proposed interleaver sets are characterized in that aninterleaver size of 2 is preferred to an interleaver size of 4 at a1.4-MHz system BW. Accordingly, RBs only, both 2 RBs and 4 RBs, or 4 RBsonly for consistency with other bands may be used as an interleaversize. As a 3-MHz system BW includes a total of 15 RBs, an interleaversize may be set to a multiple of 2 or 4 RBs. In terms of consistency,only a multiple of 4 RBs may be preferable. Especially, up to 8 or 12RBs can be supported.

An interleaver may be designed to have an interleaver size of a multipleof 5 RBs, taking into account that the number of RBs is a multiple of 5RBs (an odd number) in system BWs of 3, 5, 10, 15 and 20 MHz. However,since 4 RBs is advantageous in many aspects as stated before, a multipleof 4 RBs is preferable as an interleaver size. Since R-PDCCH PRBs occupyonly a part of total RBs, such an option as interleaving across thetotal band RBs may not be employed. Due to the existence of 25 or moreRBs in the system BW of 5 MHz or above, up to 8, 12 or 16 RBs as well as4 RBs needs to be supported. Yet, a sufficient diversity gain can beachieved from 4-RB interleaving and thus interleaving on the basis ofmore than 4 RBs is not preferred.

It may further be contemplated that an R-PDCCH is interleaved using aninterleaving depth determined according to a given system BW and mappedto PRBs. For example, if an R-PDCCH is interleaved in units of 4 RBs ina system having a 100-MHz system BW corresponding to 50 RBs, theinterleaved R-PDCCH is mapped to 4 PRBs, one PRB per RBG. For themapping, rate matching or even distribution may be used. Or bit reversalis also available. Through bit reversal, the interleaved four RBs may bemapped uniformly across the 50 RBs.

To simplify a CCE-level SS search, interleaving, and VRB-to-PRB mapping,a CCE size preferably equals to a PRB size and in addition, to a VRBsize.

[MODE FOR INVENTION]

Various embodiments have been described in the best mode for carryingout the invention.

INDUSTRIAL APPLICABILITY

The method and apparatus for transmitting and receiving an R-PDCCH beinga control channel for an RN according to the present invention areapplicable to various wireless communication systems including a 3GPPLTE system, an LTE-A system, etc.

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It is obvious tothose skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the present invention or included as a new claim by asubsequent amendment after the application is filed.

In the embodiments of the present invention, a description is made,centering on a data transmission and reception relationship among a BS,a relay, and a UE. In some cases, a specific operation described asperformed by the BS may be performed by an upper node of the BS. Namely,it is apparent that, in a network comprised of a plurality of networknodes including a BS, various operations performed for communicationwith an MS may be performed by the BS, or network nodes other than theBS. The term ‘BS’ may be replaced with the term ‘fixed station’, ‘NodeB’, ‘enhanced Node B (eNode B or eNB)’, ‘access point’, etc. The term‘UE’ may be replaced with the term ‘Mobile Station (MS)’, ‘MobileSubscriber Station (MSS)’, ‘mobile terminal’, etc.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to theembodiments of the present invention may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the embodiments of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. For example, software code may be stored in a memory unitand executed by a processor. The memory unit is located at the interioror exterior of the processor and may transmit and receive data to andfrom the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

The invention claimed is:
 1. A method for transmitting a Relay PhysicalDownlink Control Channel (R-PDCCH) by a base station (BS) in a wirelesscommunication system, the method comprising: transmitting resourceregion information indicating virtual resource blocks (VRBs) availablefor an R-PDCCH transmission to a relay node (RN) by a radio resourcecontrol (RRC) signal; mapping the VRBs to physical resource blocks(PRBs) in a resource region using a localized VRB (LVRB) mapping methodor distributed VRB (DVRB) mapping method; and transmitting R-PDCCHs tothe RN on at least one PRB of the PRBs, wherein a first R-PDCCHincluding a downlink (DL) grant is transmitted to the RN on a first slotof a subframe; wherein a second R-PDCCH including an uplink (UL) grantis transmitted to the RN on a second slot of the subframe, and whereinwhen the first R-PDCCH including the downlink (DL) grant is transmittedto the RN on the first slot of a PRB pair in the subframe, a physicaldownlink shared channel (PDSCH) for the RN is transmitted to the RN thesecond slot of the PRB pair in the subframe.
 2. The method according toclaim 1, wherein the VRBs are mapped to the PRBs so that a VRB index isone-to-one mapped to a PRB index using the localized VRB (LVRB) mappingmethod or distributed VRB (DVRB) mapping method.
 3. The method accordingto claim 1, wherein the R-PDCCH transmission is configured as a VRBunit.
 4. The method according to claim 3, wherein the size of the VRB is8 or 9 Resource Element Groups (REGs).
 5. The method according to claim2, wherein the VRBs are mapped to the PRBs by a frequency-first mappingmanner or a time-first mapping manner.
 6. The method according to claim1, further comprising: transmitting information indicating whether aninterleaving mode is applied to the R-PDCCHs, to the RN through the RRCsignal.
 7. A Base Station (BS) for transmitting a Relay PhysicalDownlink Control Channel (R-PDCCH) in a wireless communication system,the BS comprising: a transmitter; and a processor configured to cause:the transmitter to transmit resource region information indicatingvirtual resource blocks (VRBs) available for an R-PDCCH transmission toa relay node (RN) by a radio resource control (RRC) signal; and whereinthe processor is configured to map the VRBs to physical resource blocks(PRBs) in a resource region using a localized VRB (LVRB) mapping methodor distributed VRB (DVRB) mapping method, wherein the processor isfurther configured to cause: the transmitter to transmit R-PDCCHs to theRN on at least one PRB of the PRBs, the transmitter to transmit a firstR-PDCCH including a downlink (DL) grant to the RN on a first slot of asubframe, and the transmitter to transmit a second R-PDCCH including anuplink (UL) grant to the RN on a second slot of the subframe, when thetransmitter to transmit the first R-PDCCH including the downlink (DL)grant to the RN on the first slot of a PRB pair in the subframe, thetransmitter to transmit a physical downlink shared channel (PDSCH) forthe RN to the RN on the second slot of the PRB pair in the subframe. 8.The BS according to claim 7, wherein the processor is further configuredto map VRBs are mapped to the PRBs so that a VRB index is one-to-onemapped to a PRB index using the localized VRB (LVRB) mapping method ordistributed VRB (DVRB) mapping method.
 9. The BS according to claim 8,wherein the processor is further configured to map the VRBs to the PRBsby a frequency-first mapping manner or a time-first mapping manner. 10.A method for receiving a Relay Physical Downlink Control Channel(R-PDCCH) at a relay node (RN) in a wireless communication system, themethod comprising: receiving resource region information indicatingvirtual resource blocks (VRBs) available for a R-PDCCH transmission froma base station (BS) by a radio resource control (RRC) signal; monitoringthe VRBs based on the resource region information; and receivingR-PDCCHs from the BS on at least one PRB of PRBs, the VRBs are mapped tothe PRBs in a resource region using a localized VRB (LVRB) mappingmethod or distributed VRB (DVRB) mapping method, wherein a first R-PDCCHincluding a downlink (DL) grant is received from the BS on a first slotof a subframe; and wherein a second R-PDCCH including an uplink (UL)grant is received from the BS on a second slot of the subframe, andwherein when the first R-PDCCH including the downlink (DL) grant isreceived from the BS on the first slot of a PRB pair in the subframe, aphysical downlink shared channel (PDSCH) for the RN is received from theBS on the second slot of the PRB pair in the subframe.
 11. The methodaccording to claim 10, wherein the VRBs are mapped to the PRBs so that aVRB index is one-to-one mapped to a PRB index using the localized VRB(LVRB) mapping method or distributed VRB (DVRB) mapping method.
 12. Themethod according to claim 11, wherein the VRBs are mapped to PRBs by afrequency-first mapping manner or a time-first mapping manner in a PRB.13. A relay node (RN) for receiving a Relay Physical Downlink ControlChannel (R-PDCCH) in a wireless communication system, the RN comprising:a receiver; and a processor, wherein the processor is configured tocause: the receiver to receive resource region information indicatingvirtual resource blocks (VRBs) available for a R-PDCCH transmission froma base station (BS) by a radio resource control (RRC) signal; whereinthe processor is configured to monitor the VRBs based on the resourceregion information; wherein the processor is further configured tocause: the receiver to receive R-PDCCHs from the BS on at least one PRBof PRBs, the VRBs are mapped to the PRBs in a resource region using alocalized VRB (LVRB) mapping method or distributed VRB (DVRB) mappingmethod, the receiver to receive a first R-PDCCH including a downlink(DL) grant from the BS on a first slot of a subframe, and the receiverto receive a second R-PDCCH including an uplink (UL) grant from the BSon a second slot of the subframe, and when the receiver receives thefirst R-PDCCH including the downlink (DL) grant from the BS on the firstslot of a PRB pair in the subframe, the receiver receives a physicaldownlink shared channel (PDSCH) for the RN from the BS on the secondslot of the PRB pair in the subframe.
 14. The method according to claim10, further comprising: receiving information indicating whether aninterleaving mode is applied to the R-PDCCHs, from the BS through theRRC signal.